CA2109440A1 - Noise cancellation apparatus - Google Patents
Noise cancellation apparatusInfo
- Publication number
- CA2109440A1 CA2109440A1 CA002109440A CA2109440A CA2109440A1 CA 2109440 A1 CA2109440 A1 CA 2109440A1 CA 002109440 A CA002109440 A CA 002109440A CA 2109440 A CA2109440 A CA 2109440A CA 2109440 A1 CA2109440 A1 CA 2109440A1
- Authority
- CA
- Canada
- Prior art keywords
- microphone
- signal
- speech
- microphone means
- telephone handset
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
- H04R3/02—Circuits for transducers, loudspeakers or microphones for preventing acoustic reaction, i.e. acoustic oscillatory feedback
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/02—Constructional features of telephone sets
- H04M1/04—Supports for telephone transmitters or receivers
- H04M1/05—Supports for telephone transmitters or receivers specially adapted for use on head, throat or breast
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/02—Constructional features of telephone sets
- H04M1/19—Arrangements of transmitters, receivers, or complete sets to prevent eavesdropping, to attenuate local noise or to prevent undesired transmission; Mouthpieces or receivers specially adapted therefor
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/60—Substation equipment, e.g. for use by subscribers including speech amplifiers
- H04M1/6008—Substation equipment, e.g. for use by subscribers including speech amplifiers in the transmitter circuit
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/12—Neutralising, balancing, or compensation arrangements
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
- H04R2201/10—Details of earpieces, attachments therefor, earphones or monophonic headphones covered by H04R1/10 but not provided for in any of its subgroups
- H04R2201/107—Monophonic and stereophonic headphones with microphone for two-way hands free communication
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
- H04R2201/40—Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups
- H04R2201/403—Linear arrays of transducers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R29/00—Monitoring arrangements; Testing arrangements
- H04R29/004—Monitoring arrangements; Testing arrangements for microphones
- H04R29/005—Microphone arrays
- H04R29/006—Microphone matching
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
- H04R3/005—Circuits for transducers, loudspeakers or microphones for combining the signals of two or more microphones
Abstract
ABSTRACT OF THE DISCLOSURE
Apparatus for reducing acoustic background noise for use with a telephone handset or a boom microphone device or the like. The apparatus includes first and second microphones which are arranged such that the first microphone receives a desired speech input and the background noise present in the vicinity of the speech, and the second microphone receives substantially only the background noise. The background noise from the second microphone is converted into a corresponding electrical signal and subtracted from a signal corresponding to the speech and background noise obtained from the first microphone so as to produce a signal representing substantially the speech.
Apparatus for reducing acoustic background noise for use with a telephone handset or a boom microphone device or the like. The apparatus includes first and second microphones which are arranged such that the first microphone receives a desired speech input and the background noise present in the vicinity of the speech, and the second microphone receives substantially only the background noise. The background noise from the second microphone is converted into a corresponding electrical signal and subtracted from a signal corresponding to the speech and background noise obtained from the first microphone so as to produce a signal representing substantially the speech.
Description
~9~0 PATENT
NOI8E CANC~LLAT~ON APP~RAT~S
~AC~GRO~D OF T~}: INv}srlTIoN
~iol~l o~ t2~e ~nvent~ on This invention relates to a noise cancellation ~pparatus and, ~ore particularly, to an apparatus for canceling or reducing background acoustic noise for use with a telephone handset or a boom microphone device or tbe like.
D~cription o~ t~e Prior Art As is to be appreciated, in numerous situations, the presencè of background acoustic noise is undesirable. As an example, consider the situation in which an operator is attempting to conduct a telephone conversation from a telephone or such similar device located in a noisy area. In this situation, loud acoustic background noise is received by a ~icrophone in the handset of the telephone and converted to an electrical signal which is supplied to the telephone(s) of the person(s) having the conversation with the operator and is converted thereat to an acoustic signal. As a result, the person to whom the operator is communicating constantly hears the loud backqround noise. Further, when the person is speaking, such spe~ch is combined with the background noise and, as such, may b2 difficult for the other person(s) to understand. As a result, ~he operator may have to shout into ~he microphone of the telephone. Furthermore, the signal representing the background noise is also suppli~d fro~ the microphone in the operator's ~ --DS10:2020.APP
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, 2~ ~ ~ 4 ~ PA~ENT
handset to the speaXer in the operator's handset. Thus, the operator also constantly hears the background noise from the fpea~er in the operator's handset and, when the other person is speaking, may impair the understandinq thereof.
As another example, consider the situation in which a pilot who is operating a helicopter or the like wishes to communicate with another person by way of radio f-equency (RF) communication. In this situation, the pilot typically speaks into a so-called boom microphone which is couple~ to a radio transmitting/receiving device whereupon the speech is converted into ~F signals which are transmitted to a second receiving/transmitting device and converted therein to speech so as to be heard by the other person(s). As with the above situation of a telephone located in a noisy area, the loud background noise ~rom the helicopter is received and converted into an electrical signal by the boom ~i~rophone device and thereafter supplied to the receiving device. As a result, the person(s) communicating with the pilot hears the loud background noise. This may be particularly annoying when the pilot leave~
the radio transmitting/receiving device in the "ON" position while operating the helicopter.
In an attempt to reduce background noise 50 as to i~prove per~ormance of a telephone or a boom microphone located in ~ noisy environment or the like, pressure gradient microphones ~ay be utilized. Basically, a pressure gradient Dicrophone DS10:2020 .AW
~1~9d4~ PATENT
responds to the difference in pressure at two closely spaced points. When used in an environment where the pressure gradient of the bac~ground noise is isotropic, the electrical signal produced by the pressure-gradient microphone due to such 5 background noise is effectively zero. However, in most actual situations, the pressure gradient of the background noise is not isotropic and, as a result, in these situations, the performance of the pressure-gradient microphone is adversely affected.
Additionally, since voice or speech propagates in more than one direction, the electrical signal produced by the microphone ~hich corresponds thereto is often degraded. Thus, even if a pressure gradient microphone is utilized in either a telephone handset or a boom microphone, the desired amount of background noise cancellation may not be sufficient and the performance may not be adequate.
Furthermore, since two opposite sides of a pressure-gradient microphone respond to acoustic pressure, as previously ~;
mentioned, the handset of an existing telephone would have to be substantiall~ modi~ied so as to enable these two sides o~ the microphone to respond to the acoustic pressure. Moreover, as a result of u6ing such a microphone in a telephone handset, the electrical signals produced therefrom should be amplified. Thus, to replace the conventional microphone in a telephone handset of nn existing telephone with a pressure-gradient microphone would DS10:2020.APP 3 2,ln9~o PATENT
typically necessitate replacing the handset with a new handset and, ~s ~uch, would be relatively expensive.
As an alternative to using pressure-gradient ~icrophones, an acoustic feed-back type syste~ may be utilized.
Such a system normally includes compensation filters which are used to equalize the transfer function of the speakers. Since the characteristics of the speakers are tightly controlled by these filters, the cost of the filters is relatively high. As a result, such acoustic feed-back systems are typically relatively expensive.
Thus, the prior art has failed to provide a relatively low-cost means for reducing bacXground noise to an accepta~le level for use with telephones and/or boom microphone devices or the like, and a cost-effective means for enabling existing telephones to reduce background noise to an acceptable level.
OBJ~CT8_AND S~MMARY OP T~ INVENTION
An object of the present invention is to provide noise reduction apparatus which overcomes the problems associated with -~
the prior art.
~ore specifically, it is an object of the present invention to provide noise reduction apparatus which reduces background noise to an acceptable level.
Another object of the present invention is to provide noi~e reduction apparatus as aforementioned for use with a telephon2 or boo~ ~icrophone device or the like.
DS10:2020.AP$' 4 9~
PATENT
It is still another object of the present invention to provide noise reduction apparatus as aforementioned which is r~lativçly inexpensive.
It is yet another object of the present invention to provide a relatively low-cost noise reduction apparatus for use with telephones which is operable with standard available on-line power.
A still further object of the present invention is to provide a relatively low-cost noise reduction apparatus which is readily adaptable to handsets of existing telephones and which is operable with standard available on-line power.
A yet further object of the present invention is to provide a relatively low-cost noise reduction apparatus Por use with telephones or which may be readily adaptable to handsets of existing tel~phones which enables an operator to selectively amplify a received signal.
In accordance with an aspect of this invention, a .
telephone handset apparatus for use with a telephone operable by standard powsr supplied to t~e telephone handset for transmitting and receiving signals representing speech between two or ~ore operators is provided. The apparatus includes a housing haviny a first microphone means for receiving a first acoustic signal co~posed of speech from the operator using the appara~us and ,~ackground noise in the vicinity of the speech and for convexting the first acoustic ~ound to a first signal, and a s~cond D;10 :2020 .~PP 5 ' ~ , . ' :
2~o94~7~2173~18 microphone means arranged at a predetermined angle with respect to the first microphone means for receiving a second acoustic sound composed of substantially the background noise and for converting the second acoustic sound to a second signal; and a device for subtracting the second signal from the first signal ~`
so as to obtain a signal representing substantially the speech.
Other objects, features and advantages according to the present invention will become apparent from the following detailed description of the illustrated embodiments when read in conjunction with the accompanying drawings in which corres-ponding components are identified by the same reference numerals.
BRIEF DESCRIPTION OF THE DRAWINGS
:
Fig. 1 illustrates a telephone having a noise reduction apparatus according to an embodiment of the present invention;
Fig. 2 is a block diagram of the noise reduction apparatus used in the telephone of Fig. 1;
Fig. 3A is a front plan view of the receiver portion of the telephone of Fig. l;
Fig. 3B is a cross-sectional side view of the receiver portion of the telephone of Fig. 1 with the cap removed;
Fig. 4 is a schematic diagram of the block diagram of Fig. 2;
Fig. 5 is another schematic diagram of the noise reduction apparatus illustrated in Fig. 2; and Figs. 6A, 6B and 6C illustrate a boom microphone device utilizing a noise reduction apparatus according to an embodiment of the present invention.
..: `
9 4 ~l~ 72173-18 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 illustrates a telephone 8 which utilizes a noise reduction apparatus in accordance with an embodiment of the present invention. As shown therein, the telephone 8 generally includes a handset 10, having a speaker portion 41 and a receiver portion 42, and a telephone unit :L8 which may be coupled therebetween by way of a telephone cord 30. Alternatively, the telephone may be a cordless type telephone and, as such, the handset 10 is coupled to the telephone unit 18 by way of RF
waves. The receiver portion 42 includes first and second microphones 12 and 14, respectively, (Fig. 2), a switch 40 for adjusting the volume of a signal supplied to the speaker portion 41, and a cap 48 having a recessed portion 44 and a mesh portion 46.
Fig. 2 illustrates the telephone 8 in block diagram form. As shown therein, the handset 10 generally includes first and second microphones 12 and 14, respectively, a subtracting device 16, which in a preferred embodiment is an operational amplifier ("op-amp"), an amplifier 20, which is preferably an op~amp, and a speaker 22. The first and second microphones 12 and 14, respectively, op-amp 16 and amplifier 20 are preferably contained within the receiver portion 42 (see Fig. 1).
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~1 ~944~ PATENT
Acoustic signals composed of speech or the like and background noise are supplied to the first mlcrophone 12 and converted therein into a corresponding electrical signal which is thereafter supplied to the plus terminal of the op-amp 16. The background noise is supplied to the second microphone 14 and converted therein into a corresponding electrical signal which is thereafter supplied to the ~inus terminal of the op-amp 16. The op-amp 16 is adapted to subtract the noise signal from the second -microphone 14 from the speech and noise signal from the first microphone 12 and to supply therefrom an electrical signal representing substantially the speech to the telephone unit 18 whereupon the speech signal is transmitted therefrom through the telephone lines to a desir~d telephone or tel.ephones. The output signal from the op-amp 16 is also combined in the telephone unit 18 with a received signal from the telephone lines and supplied to the amplifier 20. The op-amps 16 and 17 are preferably relatively low-power integrated circuits (IC's), such as complementary metal oxide semiconductors ~CMOS), and may be constructed from either one or more CMOS IC chips. Although not 20 shown in Fig. 2, amplifier 20 may be selectively set by use of the switch 40 (Fig. 1) by the operator so as to adjust the amplification of the received signa} to a desired level, The aopli~ied ~ignal from the amplifier 20 is supplied to the speaker 22, whereupon the amplified signal is converted into an acoustic ~ignal 50 as to be heard by the operator.
DS10:2020.APP 8 ~1 ~94~0 PATENT
s50025-2020 Figs. 3A and 3B illustrate two views of the receiving portion 42, in which the cap 48 is removed in the view of Fig.
3A. As shown therein, the receiving portion 42 generally includes a housing 74, a circuit board assembly 78, the first and ~econd microphones 12 and 14, respectively, and the cap 48. The ~irst and second microphones 12 and 14, respectively, which are ~ :
preferably electret microphones or similar such microphones, are arranged or positioned as hereinafter described. These microphones are held in place or secured by a holding member 76 wh~ch, for example, may be constructed of a foam-like material, which, in turn, is secured to the housing 74. The respective outputs from the first and second microphones 12 and 14 are supplied through respective wires (not shown) to the op~amp 16 which is contained on the circuit board assembly 78 which, in turn, is attached to the housing 74. As hereinafter more fully described, the circuit board 78 may contain additional circuit elements for processing the signals received fro~ the first and second microphones and for amplifying si~nals for supply to the speaker 22 (Fig.2). A cover 72 may be utilized which is attached to the hou~ing 74 by use of ~dhesives or the liXe or alternatively may be sonically welded together. The cover 72 and the hou ing 74 with the circuit board assembly 78, holding member 76 and the first and second microphones 12 and 14 form an ~sembly 71.
DS10:20ZO.APP 9 ' ' '' ' ~ '' `
~09~40 pATENT
5s00z5-2020 The cap 48, which may be constructed from a plastic-type material such as polycarbonate, includes an annular side ~ beir 43 and a portion 45 having a typical thickne~s T which is coupled to the side member 43 and arranged so as to be lower than the upper portion of the side member by a minimum predetermined a~Sount such as 0.020 of an inch, thereby creatins a recessed portion 44. The portion 45 includes a portion 46 having a thickness T' which is less than the thickness T and which has a plurality of through holes contained therein and may resemble a mesh-like portion. In a preferred embodiment, the thickness T' of the portion 46 has a thickness of less than 0.030 of an inch.
Since the portion 46 represents a relatively small a~ount of the portion 45, reducing the thickness therein does not adversely affect the overall structural rigidity of the cap 48.
Alternatively, the portion 46 may be constructed from a stronger material, for example, stainless steel or such similar material, and combined with the portion 45. As is to be appreciated, ~y arrangin~ the portions 45 and 46 so as to be recessed from the upper portion o~ the side member 4~3, even when the receiver ::
portion 42 is placed on a surface, the side member 43, and not the portions 45 or 46, contact such surface. As a result, any :~-loads are not directly impacted on the portion 45 and/or the : --portion 46, but are instead delivered to the side member 43.
The cap 48 is positioned over the asse~bly 71 so that ;~
the first and second microphones 12 and 14, respectively, are -~
D510:2020.APP 10 -: . :
21 09~0 PATENT
arranged below the portion 46 with the first microphone positioned relatively close to the underside of the portion 46 Thus, the speech travels a relatively short distance from an operator, who is speaking into the receiver portion 42 from a S distance of preferably less than 1 inch, through the portion 46 to the first microphone. As a result, acoustic ~istortions are minimized.
The arrangement of the first and second microphones 12 and 14, respectively, within the receiver portion 42 is illustrated in Figs. 3A and 3B. More specifically, as shown in Fig. 3B, the first and second microphones are arranged so as to have an angle 0 therebetween, which preferably has a value in a range bQtween 30 and 60. The first and second microphones are further respectively arranged so as to have an angle e and [(gO-e) + o] between a plane parallel to the receiving or "sensitive"surface of the first microphone 12 and the direction of speech from an operator, and an axis normal to the sensitive surface of the second microphone 14 and the direction of speech, as shown in Fig. 3~; and so as to have an angle ~ between the direction of ~peech and the second microphone, as shown in Fig. 3A. In a preferred e~bodiment, the angle e has a value of less than approximately 35 and the angle ~ has a value of approximately 180. As a result of arranging the first and second microphones ~n this manner, the ~irst ~icrophone 12 receives both the speech from the operator and the background acoustic noise which is DS10:Z020.~
'', .,:, : ~'' 21~9~4~ PATENT
present in the vicinity, and the second microphone 14 essentially receives only the same background acoustic noise which is r~ceived by the first microphone.
Although, as previously mentioned, the angle 0 has a value which is preferably between 30 and 60, the first and second microphones 12 and 14, respectively, may nevertheless operate satisfactorily even if arranged so as to have an angle 0 which lies outside this range. However, as the angle 0 becomes substantially smaller than 30 or larger than 60, the performance may be adversely affected. That is, when the angle 0 becomes substantially smaller than 30, the second microphone 14 receives both the speech and background noise. As a result, upon subtracting the output signal of the second microphone 14 from the output signal of the first m~crophone 12, a portion or all of ~ ~
the speech may be canceled. On the other hand, when the angle 0 ~:
is substantially larger than 60, the background noise received by the second microphone 14 may not be similar to that received -~
by the first microphone 12. As a result, subtracting the output -siqnal of the second microphone 14 from the output signal of the first microphone 12 may not adequately cancel the background noise received by the first ~icrophone.
In a like manner, although the angles ~ and ~ have ;
preferred values of less than 35 and approximately 180, -~
raspectively, as previously ~e~tioned, the first and second nicrophones may operate satis~actorily even if arranged so as to -~
DSl0:2020.APP 12 .. ~
: ~ :
~1 09~40 PATENT
present in the vicinity, and the second microphone 14 essentially receives only the same background acoustic noise which is r~ceived by the first microphone.
Although, as previously mentioned, the angle 0 has a value which is preferably between 30 and 60, the first and ~econd microphones 12 and 14, respectively, may nevertheless operate satisfactorily even if arranged so as to have an angle 0 which lies outside this range. However, as the angle 0 becomes substantially smaller than 30 or larger than 60, the performance may be adversely affected. That is, when the angle 0 becomes su~stantially smaller than 30, the second microphone ~4 receives both the speech and background noise. As a result, upon subtracting the output signal of the second microphone 14 from the output signal of the first microphone 12, a portion or all of the speech may be canceled. On the other hand, when the angle 0 is substantially larger than 60, the background noise received by the second microphone 14 may not be similar to that received by the first microphone 12. As a result, subtracting the output signal of the second microphone 14 from ~he output signal of the ~-first ~icrophone 12 may not adequately cancel the background nois~ received by the first microphone.
In a like ~anner, although th~ angles ~ and ~ have preferred values of less than 359 and approximately 180, respectively, as previously mentioned, the first and second ~5 microphones may op~rate satisfactorily even if arranged so as to OS10:2020,APF~ 12 :, ` ~, :
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21~9440 PATENT
have different values of these angles. However, as th~ values of ~he angles ~ and ~ become substantially different from the respective preferred values, the performance may be adversely ~ffected. That is, when the angle ~ becomes substantially larger than 35 , the second microphone 14 may receive both the speech and background noise. Similarly, when the angle ~ is substantially smaller or larger than 180, the second microphone 14 may receive both the speech and background noise. As a result, in either of these situations, upon subtracting the output signal of the second microphone 14 from the output signal ~E the first microphone 12, a portion or even all of the speech may be canceled.
As is to be appreciated, by using the above-described ~ ;
devices and materials for the components of the receiver portion 42, the cost for constructing such receiver portion is relatively low. Further, by using CMOS chips, as previously described, the power consumption of the receiver portion is kep~ relatively low.
As a result, the receiver portion may be powered by the standard power available in the handset and, as such, does not require additional power or transformers or the like. Furthermore, although the receiver portion 42 has been described for assembly with the handset 10 of the telephone 8, which is a new telephqne~
such r~ceiver portion, or a slight variation thereof, may be used ln handsets of existing telephones. ~hat is, in this latter situation, the cap and microphone contained within the handset of DglO:2020.APP 1 3 PATENT
an existing telephone are merely replàced with the receiver portion 42. Thus, such use of the receiver portion 42 provides a rolatively easy and low-cost means to modif~ a handset of an ` ~xisting telephone to include the present noise reduction apparatus.
Fig. 4 illustrates a schematic diagram of one circuit arrangement of the telephone 8 shown in Figs. 'L and 2. As shown in Fig. 4, the first microphone 12 is coupled through a resistor -202, which is adapted to function as a current limiting resistor so as to correct the bias of an output ~rom the first microphone, to an input terminal 200. The first microphone 12 is further coupled through a resistor 210 to the plus terminal of the op-amp 16 and through a resistor 212 to a variable resistor 214. The sacond microphone 14 is coupled through a variable resistor 208, which is adapted to function as a current limiting resistor so as to correct the bias of an output of the second microphone, to an input terminal 201, and to the minus terminal of the op-amp 16.
The limiting resistor 208 is preferably a variable current limiting resistor which enables the level of the output signal from the second microphone to be matched to within a predetermined value to the level of the output signal of thP
first ~icrophone 12. More specifically, the limiting resistor 208 enables the output signal of the second microphone 14 to be weighted such that when a signal havin~ a similar level is outputted from the first microphone 12, the amplitude of the DS10:2~.APD 14 .
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~,109440 PATENT
di~f~irence therebetween is minimized. The value of the current limiting resistor 208 can be selected according to minimization criteria. An input terminal 198 is connected to resistors 204 ~nd 206, which are adapted to divide the voltage received at the ~nput terminal 198, and to the minus terminal of the op-amp 16.
The output of the op-amp 16 is coupled to capacitors 220, 222 and 226 and resistors 224 and 228 which, in turn, is connecte,i to a nmicrophone input" terminal of the telephone unit 18. The output : -:
from the op-amp 16 is further coupled through a variable resistor ~- -214, a resistor 216 and a capacitor 218 to ground. Resistors ~ ~-210, 212 and 216 and variable resistor 214 provide variable gain, ~
.
for example, 20 to 1 amplification, to the output o~' the op-amp 16. 'I'he capacitors 218, 220 and 222 are adapted to remove residual dc (direct current) levels which may be present in the output signal from the op-amp 16. The resistors 224 and 228 and the capacitor 226 are adapted to function as a low-pass filter having a break point at a predetermined value which, for example, may be 3.7 ~Hz.
Th,a t~lephone unit 18 is further connected to the telephone lines and i5 adapted to receive signals through the ~icrophone input ter~inal and to supply these signals to the desired teilephone or telephones by way of the telephone lines.
'The telephone unit 18 is further adapted to receive signals from anothier telephone or telephones by way of the telephone lines and to co~bine such signals with thiose received through the DS10:2020.APP 15 . ~
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Z1~9~4~
PATENT
~ microphone input terminal, as previously described, and to supply .~ ~he combined signal to a speaker input terminal 231. ~he input .~ torminal 231 is connected through a capacitor 230, which is .' ~dapted to block dc signals, and a resistor 232 to the minug terminal of an op-amp 17 and through a resistor 234 to a variable resistor 240. An input terminal 199 is connected to the plus terminal of the op-amp 17. The output from the op-amp 17 is connected through capacitors 242 and 244 and a resistor 246 to the speaker 22. T~e output from the op-amp is further connected through the variable resistor 240, a resistor 238 and a capacitor 236 to ground.
` The operation of the telephone 8 shown in Fig. 4 will now be described below.
Upon activating the handset 10, by lifting the handset ~`;; lS 10 from the switch hook (not shown) or the like, standard telephone line voltage is applied to input terminals 198, 199, ~` 200 and 201. A signal fro~ the first microphone 12, which has ~,i been bias corrected by the current limiting resistor 202, is ~` supplied through the resistor 210 to ~he plus terminal of the op-~` 20 amp 16. An output signal from the second microphone 14, which has ~een bias corrected by the current limiting resistor 208, is ~r supplied to the minus terminal of the op-amp 16. The op-amp 16 ~ubtracts the signal received from the second microphone 14 from that received from the first microphone 12 and outputs the 2S resulting subtracted signal. DC levels which may be present in ~Sl0:2020.API> 16 ' ~-~
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st, ~, , . ~ ` -21 0 9 ~ ~ O PATENT
the output signal are removed and the signal is amplified. High ~requency signals, such as those over 3.7 kHz, are then removed -~
fro~ the amplified output signal and the resulting signal is ; upplied to the telephone unit 18. Thus, a voltage signal is ~ -supplied to the telephone unit 18 which is proportional to the difference between the voltages generated by the first and second ~icrophones 12 and 14, respectively.
An output signal from the telephone unit 18, which is a -~
combination of the signals received through the microphone input -~ ~
10 terminal and the telephone lines, is supplied to the input -terminal 231 of the amplifier 20. The signal from the input terminal 231 is supplied to the capacitor 230 so as to remove any dc signals which may be present. The output from the capacitor 230 is supplied through the resistor 232 to the minus terminal of ` 15 the op-amp 17. The op-amp 17 subtracts the signal from the : -telephone unit 18 from the signal received from the input terminal 199 and supplies a subtracted signal therefrom. Such signal may be selectively amplified, through the use o~ resistors ;
232, 234 and 238 and variable resistor 2~0, by the operator by use of the switch 40 (Fig. 1). Any dc signals which may be present in the amplified signal are thereafter removed by the ; capacitors 242, 244 and 236. The output signal from the capacitor 244 is current li~ited by the resistor 24~ and is thereafter supplied to the speaker 22 so as to be converted thereat into an acoustic signal.
DS10:20ZO.APP 17 : ;
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~1~9~
PATENT
Fig. 5 illustrates an alternative arrangement for processlng the signals obtained from the first and second ~$crophones 12 and 14, respectively, so as to provide a current - output for supp}y to the telephone unit 18 which is proportional 5 to the difference of the voltaqes generated by the first and second microphones.
More specifically, the circuit arrangement of Fig. 5 includes a handset 10' having a plurality of input terminals 300, 301, 370 and 390 which are each adapted to receive standard available on-line power. The first microphone 12 is coupled ' through a current limiting resistor 302 to the input terminal 300 and is further coupled to the plus terminal of a subtracting device 316, which is pre~erably a CMOS op-amp. The output from the second microphone 14 is coupled through a variable current limiting resister 308 to the input terminal 301 and is further ~oupled to the minus terminal of the op-amp 316. The signal -outputted from the op-amp 316 is supplied through filtering - stages 350 to the minus terminal of a subtracting device 351 which is preferably a CMOS op-amp. The filtering stages 350 are adapted to provide a predetermined frequency response characteristic such as a signal roll off at a predetermined frequency. As is to be appreciated, although two filtering stages are ~hown in Fig. S any number of ~iltering stages may be utilized. The input terminal 390 is coupled to resistors 392 and , 25 394, which are adapted to reduce the signal supplied thereto, and Dsl0:2020.~PP 18 .` ' , .
. ~
- , , , ; ,: ~, ~ : , , : :
t h 10 9 4 ~1~ PATENT
to the plus terminal of the op-amp 351. An output signal from . the op-amp 351 is supplied to the base of a transistor 366. The input ter~inal 391 is connected to a Zener diode 360, a capacitor . , 362 and a resistor 364 which, in turn, is connçcted to the . S collector of the transistor 366 and to the microphone input terminal of the telephone unit 18. The emitter of the transistor 366 is coupled through resistors 367 and 368 to the minus :~
terminal of the op-amp 351 so as o provide a ~eedback loop ~` thereto. The op-amp 351 and the associated components provide -~
electrical isolation between the filtering stages 350 and the transistor 366. The transistor 366 is adapted to amplify the signal supplied to the telephone unit 18.
~; The output from the telephone unit 18 is coupled to the input terminal 231 ~Fig. 4) and is thereafter processed in the manner previously described with reference to the handset 10 of Fig. 4 so as to provide an acoustic signal from the speaker 22.
The operation of the telephone 8' will now be described b~low.
Upon applying power to the handset 10', by lifting the handset ~rom the switch hook (not shown) or the like, standard ~` telephone line voltage is applied to input terminals 300, 301, ,` 370, 390 and 391. A signal from the first microphone 1~, which ' haQ been bias corrected by the current }imiting resistor 302, is ~upplied to the plus terminal o~ the op-amp 316. An output 25 - oignal from the second microphone 14, which has been bias S DS10:2020.APP 19 :
., .
', ? : . . :
21~9~0 PATENT
corracted by the current limiting resistor 308, is supplied to the minus terminal of the op-amp 316. The resistor 308 i5 pre~erably a variably current limiting resistor which enables the l~vel of the output signal from the second microphone 14 to be matched to within a predetermined value to the level of the ; output signal of the first microphone 12, in a manner substantially similar to that previously described for resistor 208. The output difference signal from the op-amp 316 is provided though the filtering stages 350, which may include one or more RC networks or equivalent circuits, so as to limit the upper frequency of the output signal to a predetermined value which, for example, may be 3.7 kHz. The output signal from the ~iltering stages 350 is supplied to the minus terminal o the op-amp 351 and a voltage signal from the input terminal 390, which ` 15 has been divided to a predetermined value such as one half ` thereof, is supplied to the plus terminal of the op-amp 351 which, in turn, calculates the di~ference therebetween and supplies a corresponding output signal to the base of the transistor 366. The voltage from the input terminal 391 is supplied through the resis~or 364 to ~he collector of the transistor 366. As a result, an amplified signal is supplied from the handset 10' to the telephone unit 18 for supply i t~erefrom through the telephone }ines to the desired telephone(s) nd for combining with a received si~nal from the te}ephone(s) .
DS10:2--0.AW 2 0 ~ .
- ` 21~944~ ~
PATENT
for 8Upply to the input terminal 231 in a manner similar to that previously described with reference to Fig. 4.
The individual circuit components wit:hout reference d~signations depicted in Figs. 4 and 5 are connected as shown and will not be discussed further, since the connec:tions and values ~re apparent to those s~illed in the art and are not necessary ,~ for an understanding of the present invention.
i Figs. 6A, 6~ and 6C illustrate a boom microphone 100 which utilizes a noise cancellation apparatus in accordance with an embodiment of the present invention. More specifically, the boom microphone 100 generally includes a housing 174, a circuit board assembly 178, first and second microphones 112 and 114, respectively, and a portion 147. The housing 174, which may be constructed from either a plastic-like or metal-type material, includes a circular portion 108 having a hole therethrough so as ~,~ to enable a shaft 106 to be inserted therein. As a result, the ` boom microphone 100 may rotate about the shaft 106 as illustrated -` in Fig. 6A.
The first and second microphones 112 and 114 are respectively coupled to the circuit board assembly 178 by wires 102 and 104. Tha circuit board assembly 178 contains circuitry similar to that on the circuit board assembly 78 which, as - previously described, processes the signals from the first and ~econd microphones 12 and 14, respectively, for supply to the telephone unit 18 and, as such, in the interest of brevity, will j~ DslO:20Xl.APP 21 ! ' i;` :
. .' . .
21~9~40 , PATENT
not be further described herein. Therefore, the circuit board aA~embly 178 is adapted to receive a speech and bac~ground noise ~ignal from the first microphone 112 and to subtract therefrom the background noise signal from the second microphone 114 so as to derive a signal which represents substantially the speech.
Such signal is supplied to a transmitting device (not shown) so as to be converted to a RF signal and transmitted to a remote receiving device (not shown). The first and second microphones 112 and 114, respectively, are held in place by a holding member 176 which, for example, ~ay be constructed of a foam-like material. A mesh~ e screen 146 which, for example, may be fabricated from a plastic-type or a metal mat~rial or the like, is attached to the cut away portion 147 so as to protect the ; first and second microphones. The mesh 146 has a predetermined ~ 15 thicknQs~ which, for example, may be approximately 0.030 or less `i, of an inch.
The first and second microphones 112 and 114, respectively, whieh may be electret microphones, are arranged in ~! a ~anner similar to that of the pr~viously described first and .
second microphones 12 and 14, respectively, of the handset 10.
That is, the first and second microphones 112 and 11~, are ~` r~spectively positioned so as to have an angle e~ and [(9o-e~) +
,~ o'~ between a plane parallel to the receiving or sensitive urface of the first ~icrophone and the direction of speech from an operator, and between an axis normal ~o the sensitive surface D510:2020.~PP 22 ?, 9~40 PATENT
of the second microphone and the direction of speech, as shown in Fig. 5A. Further, the first and second microphones 112 and 114, respectively, are arranged so as to have an angle 0' therebetween, which has a preferred value in a range between 30O
and 60. The first and second microphones 112 and 114, respectively, are located in relatively close proximity to the ~esh 146 and the cut away portion 147 of the housing 174 so as not to receive acoustic sounds which have ~een unacceptably distorted.
Although the above embodiments have been described as having only one first microphone 12 (112) and one second microphone 14 (114), the invention is not so limited and any number of microphones may be utilized for the first microphone and/or the second microphone. For example, a receiver portion 42' (not shown) may be configured which includes two or more microphones operating as a first microphone 12' (not shown) and two or ~ore microphones operating as a second microphone 14' (not shown). In this configuration, when using multiple microphones for the first and/or second microphones, respective variable current limiting resistors are preferably provided for all but one micropho~e for the first microphone 12' and for all microphones for th~ second ~icrophone 14'. Thus, the outputs from the first and second microphones, 12' and 14', respectively, would comprise a weighted sum of several such microphone output voltages. The current limiting resistors are preferably set to DS10:2020.APP 23 .
, ~:
:' . .
`` ~109~40 PATENT
respective values so as to minimize some functlonal of the l~ diff~rence of the first and second microphones 12' and 14', respectively. The criterion for selecting the values of the current limiting resistor or equivalently the weighting function Y' of ~ach microphone could be selected according to any well known gradient search algorithm, so as to minimize the functional.
Further, although the above-described embodiments of the present inventisn have been described for use with telephone handsets and boom microphones and the like, the present invention is not so limited and may be used with numerous other devices such as intercom systems and so forth. Additionally, the present 1`
invention ~ay be used with processing devices operating in ,!' accordanc~ with predetermined processing algorithms, as described i`l in U.S. Ratent Application Serial No. 07/887,500 filed May 22, 1992, which has a common assignee with the present application, and which is hereby incorporated by reference.
Furthermore, although preferred embodiments of the present invention and modifications thereof have b~en described in detail herein, it is to be understood that this invention is not limited to those precise embodiments and modifications, and ~ that other modifications and variations may be affected by one i ~killed in the art without departing from he spirit and scope of ~ th~ invention as defined by the appended claims.
.:
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DslO:2020.. ~PP 2 4 ~`
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NOI8E CANC~LLAT~ON APP~RAT~S
~AC~GRO~D OF T~}: INv}srlTIoN
~iol~l o~ t2~e ~nvent~ on This invention relates to a noise cancellation ~pparatus and, ~ore particularly, to an apparatus for canceling or reducing background acoustic noise for use with a telephone handset or a boom microphone device or tbe like.
D~cription o~ t~e Prior Art As is to be appreciated, in numerous situations, the presencè of background acoustic noise is undesirable. As an example, consider the situation in which an operator is attempting to conduct a telephone conversation from a telephone or such similar device located in a noisy area. In this situation, loud acoustic background noise is received by a ~icrophone in the handset of the telephone and converted to an electrical signal which is supplied to the telephone(s) of the person(s) having the conversation with the operator and is converted thereat to an acoustic signal. As a result, the person to whom the operator is communicating constantly hears the loud backqround noise. Further, when the person is speaking, such spe~ch is combined with the background noise and, as such, may b2 difficult for the other person(s) to understand. As a result, ~he operator may have to shout into ~he microphone of the telephone. Furthermore, the signal representing the background noise is also suppli~d fro~ the microphone in the operator's ~ --DS10:2020.APP
,.
, 2~ ~ ~ 4 ~ PA~ENT
handset to the speaXer in the operator's handset. Thus, the operator also constantly hears the background noise from the fpea~er in the operator's handset and, when the other person is speaking, may impair the understandinq thereof.
As another example, consider the situation in which a pilot who is operating a helicopter or the like wishes to communicate with another person by way of radio f-equency (RF) communication. In this situation, the pilot typically speaks into a so-called boom microphone which is couple~ to a radio transmitting/receiving device whereupon the speech is converted into ~F signals which are transmitted to a second receiving/transmitting device and converted therein to speech so as to be heard by the other person(s). As with the above situation of a telephone located in a noisy area, the loud background noise ~rom the helicopter is received and converted into an electrical signal by the boom ~i~rophone device and thereafter supplied to the receiving device. As a result, the person(s) communicating with the pilot hears the loud background noise. This may be particularly annoying when the pilot leave~
the radio transmitting/receiving device in the "ON" position while operating the helicopter.
In an attempt to reduce background noise 50 as to i~prove per~ormance of a telephone or a boom microphone located in ~ noisy environment or the like, pressure gradient microphones ~ay be utilized. Basically, a pressure gradient Dicrophone DS10:2020 .AW
~1~9d4~ PATENT
responds to the difference in pressure at two closely spaced points. When used in an environment where the pressure gradient of the bac~ground noise is isotropic, the electrical signal produced by the pressure-gradient microphone due to such 5 background noise is effectively zero. However, in most actual situations, the pressure gradient of the background noise is not isotropic and, as a result, in these situations, the performance of the pressure-gradient microphone is adversely affected.
Additionally, since voice or speech propagates in more than one direction, the electrical signal produced by the microphone ~hich corresponds thereto is often degraded. Thus, even if a pressure gradient microphone is utilized in either a telephone handset or a boom microphone, the desired amount of background noise cancellation may not be sufficient and the performance may not be adequate.
Furthermore, since two opposite sides of a pressure-gradient microphone respond to acoustic pressure, as previously ~;
mentioned, the handset of an existing telephone would have to be substantiall~ modi~ied so as to enable these two sides o~ the microphone to respond to the acoustic pressure. Moreover, as a result of u6ing such a microphone in a telephone handset, the electrical signals produced therefrom should be amplified. Thus, to replace the conventional microphone in a telephone handset of nn existing telephone with a pressure-gradient microphone would DS10:2020.APP 3 2,ln9~o PATENT
typically necessitate replacing the handset with a new handset and, ~s ~uch, would be relatively expensive.
As an alternative to using pressure-gradient ~icrophones, an acoustic feed-back type syste~ may be utilized.
Such a system normally includes compensation filters which are used to equalize the transfer function of the speakers. Since the characteristics of the speakers are tightly controlled by these filters, the cost of the filters is relatively high. As a result, such acoustic feed-back systems are typically relatively expensive.
Thus, the prior art has failed to provide a relatively low-cost means for reducing bacXground noise to an accepta~le level for use with telephones and/or boom microphone devices or the like, and a cost-effective means for enabling existing telephones to reduce background noise to an acceptable level.
OBJ~CT8_AND S~MMARY OP T~ INVENTION
An object of the present invention is to provide noise reduction apparatus which overcomes the problems associated with -~
the prior art.
~ore specifically, it is an object of the present invention to provide noise reduction apparatus which reduces background noise to an acceptable level.
Another object of the present invention is to provide noi~e reduction apparatus as aforementioned for use with a telephon2 or boo~ ~icrophone device or the like.
DS10:2020.AP$' 4 9~
PATENT
It is still another object of the present invention to provide noise reduction apparatus as aforementioned which is r~lativçly inexpensive.
It is yet another object of the present invention to provide a relatively low-cost noise reduction apparatus for use with telephones which is operable with standard available on-line power.
A still further object of the present invention is to provide a relatively low-cost noise reduction apparatus which is readily adaptable to handsets of existing telephones and which is operable with standard available on-line power.
A yet further object of the present invention is to provide a relatively low-cost noise reduction apparatus Por use with telephones or which may be readily adaptable to handsets of existing tel~phones which enables an operator to selectively amplify a received signal.
In accordance with an aspect of this invention, a .
telephone handset apparatus for use with a telephone operable by standard powsr supplied to t~e telephone handset for transmitting and receiving signals representing speech between two or ~ore operators is provided. The apparatus includes a housing haviny a first microphone means for receiving a first acoustic signal co~posed of speech from the operator using the appara~us and ,~ackground noise in the vicinity of the speech and for convexting the first acoustic ~ound to a first signal, and a s~cond D;10 :2020 .~PP 5 ' ~ , . ' :
2~o94~7~2173~18 microphone means arranged at a predetermined angle with respect to the first microphone means for receiving a second acoustic sound composed of substantially the background noise and for converting the second acoustic sound to a second signal; and a device for subtracting the second signal from the first signal ~`
so as to obtain a signal representing substantially the speech.
Other objects, features and advantages according to the present invention will become apparent from the following detailed description of the illustrated embodiments when read in conjunction with the accompanying drawings in which corres-ponding components are identified by the same reference numerals.
BRIEF DESCRIPTION OF THE DRAWINGS
:
Fig. 1 illustrates a telephone having a noise reduction apparatus according to an embodiment of the present invention;
Fig. 2 is a block diagram of the noise reduction apparatus used in the telephone of Fig. 1;
Fig. 3A is a front plan view of the receiver portion of the telephone of Fig. l;
Fig. 3B is a cross-sectional side view of the receiver portion of the telephone of Fig. 1 with the cap removed;
Fig. 4 is a schematic diagram of the block diagram of Fig. 2;
Fig. 5 is another schematic diagram of the noise reduction apparatus illustrated in Fig. 2; and Figs. 6A, 6B and 6C illustrate a boom microphone device utilizing a noise reduction apparatus according to an embodiment of the present invention.
..: `
9 4 ~l~ 72173-18 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 illustrates a telephone 8 which utilizes a noise reduction apparatus in accordance with an embodiment of the present invention. As shown therein, the telephone 8 generally includes a handset 10, having a speaker portion 41 and a receiver portion 42, and a telephone unit :L8 which may be coupled therebetween by way of a telephone cord 30. Alternatively, the telephone may be a cordless type telephone and, as such, the handset 10 is coupled to the telephone unit 18 by way of RF
waves. The receiver portion 42 includes first and second microphones 12 and 14, respectively, (Fig. 2), a switch 40 for adjusting the volume of a signal supplied to the speaker portion 41, and a cap 48 having a recessed portion 44 and a mesh portion 46.
Fig. 2 illustrates the telephone 8 in block diagram form. As shown therein, the handset 10 generally includes first and second microphones 12 and 14, respectively, a subtracting device 16, which in a preferred embodiment is an operational amplifier ("op-amp"), an amplifier 20, which is preferably an op~amp, and a speaker 22. The first and second microphones 12 and 14, respectively, op-amp 16 and amplifier 20 are preferably contained within the receiver portion 42 (see Fig. 1).
, ', ~ . '.' , , ~' '' - ~ , , .. ..
.
~1 ~944~ PATENT
Acoustic signals composed of speech or the like and background noise are supplied to the first mlcrophone 12 and converted therein into a corresponding electrical signal which is thereafter supplied to the plus terminal of the op-amp 16. The background noise is supplied to the second microphone 14 and converted therein into a corresponding electrical signal which is thereafter supplied to the ~inus terminal of the op-amp 16. The op-amp 16 is adapted to subtract the noise signal from the second -microphone 14 from the speech and noise signal from the first microphone 12 and to supply therefrom an electrical signal representing substantially the speech to the telephone unit 18 whereupon the speech signal is transmitted therefrom through the telephone lines to a desir~d telephone or tel.ephones. The output signal from the op-amp 16 is also combined in the telephone unit 18 with a received signal from the telephone lines and supplied to the amplifier 20. The op-amps 16 and 17 are preferably relatively low-power integrated circuits (IC's), such as complementary metal oxide semiconductors ~CMOS), and may be constructed from either one or more CMOS IC chips. Although not 20 shown in Fig. 2, amplifier 20 may be selectively set by use of the switch 40 (Fig. 1) by the operator so as to adjust the amplification of the received signa} to a desired level, The aopli~ied ~ignal from the amplifier 20 is supplied to the speaker 22, whereupon the amplified signal is converted into an acoustic ~ignal 50 as to be heard by the operator.
DS10:2020.APP 8 ~1 ~94~0 PATENT
s50025-2020 Figs. 3A and 3B illustrate two views of the receiving portion 42, in which the cap 48 is removed in the view of Fig.
3A. As shown therein, the receiving portion 42 generally includes a housing 74, a circuit board assembly 78, the first and ~econd microphones 12 and 14, respectively, and the cap 48. The ~irst and second microphones 12 and 14, respectively, which are ~ :
preferably electret microphones or similar such microphones, are arranged or positioned as hereinafter described. These microphones are held in place or secured by a holding member 76 wh~ch, for example, may be constructed of a foam-like material, which, in turn, is secured to the housing 74. The respective outputs from the first and second microphones 12 and 14 are supplied through respective wires (not shown) to the op~amp 16 which is contained on the circuit board assembly 78 which, in turn, is attached to the housing 74. As hereinafter more fully described, the circuit board 78 may contain additional circuit elements for processing the signals received fro~ the first and second microphones and for amplifying si~nals for supply to the speaker 22 (Fig.2). A cover 72 may be utilized which is attached to the hou~ing 74 by use of ~dhesives or the liXe or alternatively may be sonically welded together. The cover 72 and the hou ing 74 with the circuit board assembly 78, holding member 76 and the first and second microphones 12 and 14 form an ~sembly 71.
DS10:20ZO.APP 9 ' ' '' ' ~ '' `
~09~40 pATENT
5s00z5-2020 The cap 48, which may be constructed from a plastic-type material such as polycarbonate, includes an annular side ~ beir 43 and a portion 45 having a typical thickne~s T which is coupled to the side member 43 and arranged so as to be lower than the upper portion of the side member by a minimum predetermined a~Sount such as 0.020 of an inch, thereby creatins a recessed portion 44. The portion 45 includes a portion 46 having a thickness T' which is less than the thickness T and which has a plurality of through holes contained therein and may resemble a mesh-like portion. In a preferred embodiment, the thickness T' of the portion 46 has a thickness of less than 0.030 of an inch.
Since the portion 46 represents a relatively small a~ount of the portion 45, reducing the thickness therein does not adversely affect the overall structural rigidity of the cap 48.
Alternatively, the portion 46 may be constructed from a stronger material, for example, stainless steel or such similar material, and combined with the portion 45. As is to be appreciated, ~y arrangin~ the portions 45 and 46 so as to be recessed from the upper portion o~ the side member 4~3, even when the receiver ::
portion 42 is placed on a surface, the side member 43, and not the portions 45 or 46, contact such surface. As a result, any :~-loads are not directly impacted on the portion 45 and/or the : --portion 46, but are instead delivered to the side member 43.
The cap 48 is positioned over the asse~bly 71 so that ;~
the first and second microphones 12 and 14, respectively, are -~
D510:2020.APP 10 -: . :
21 09~0 PATENT
arranged below the portion 46 with the first microphone positioned relatively close to the underside of the portion 46 Thus, the speech travels a relatively short distance from an operator, who is speaking into the receiver portion 42 from a S distance of preferably less than 1 inch, through the portion 46 to the first microphone. As a result, acoustic ~istortions are minimized.
The arrangement of the first and second microphones 12 and 14, respectively, within the receiver portion 42 is illustrated in Figs. 3A and 3B. More specifically, as shown in Fig. 3B, the first and second microphones are arranged so as to have an angle 0 therebetween, which preferably has a value in a range bQtween 30 and 60. The first and second microphones are further respectively arranged so as to have an angle e and [(gO-e) + o] between a plane parallel to the receiving or "sensitive"surface of the first microphone 12 and the direction of speech from an operator, and an axis normal to the sensitive surface of the second microphone 14 and the direction of speech, as shown in Fig. 3~; and so as to have an angle ~ between the direction of ~peech and the second microphone, as shown in Fig. 3A. In a preferred e~bodiment, the angle e has a value of less than approximately 35 and the angle ~ has a value of approximately 180. As a result of arranging the first and second microphones ~n this manner, the ~irst ~icrophone 12 receives both the speech from the operator and the background acoustic noise which is DS10:Z020.~
'', .,:, : ~'' 21~9~4~ PATENT
present in the vicinity, and the second microphone 14 essentially receives only the same background acoustic noise which is r~ceived by the first microphone.
Although, as previously mentioned, the angle 0 has a value which is preferably between 30 and 60, the first and second microphones 12 and 14, respectively, may nevertheless operate satisfactorily even if arranged so as to have an angle 0 which lies outside this range. However, as the angle 0 becomes substantially smaller than 30 or larger than 60, the performance may be adversely affected. That is, when the angle 0 becomes substantially smaller than 30, the second microphone 14 receives both the speech and background noise. As a result, upon subtracting the output signal of the second microphone 14 from the output signal of the first m~crophone 12, a portion or all of ~ ~
the speech may be canceled. On the other hand, when the angle 0 ~:
is substantially larger than 60, the background noise received by the second microphone 14 may not be similar to that received -~
by the first microphone 12. As a result, subtracting the output -siqnal of the second microphone 14 from the output signal of the first microphone 12 may not adequately cancel the background noise received by the first ~icrophone.
In a like manner, although the angles ~ and ~ have ;
preferred values of less than 35 and approximately 180, -~
raspectively, as previously ~e~tioned, the first and second nicrophones may operate satis~actorily even if arranged so as to -~
DSl0:2020.APP 12 .. ~
: ~ :
~1 09~40 PATENT
present in the vicinity, and the second microphone 14 essentially receives only the same background acoustic noise which is r~ceived by the first microphone.
Although, as previously mentioned, the angle 0 has a value which is preferably between 30 and 60, the first and ~econd microphones 12 and 14, respectively, may nevertheless operate satisfactorily even if arranged so as to have an angle 0 which lies outside this range. However, as the angle 0 becomes substantially smaller than 30 or larger than 60, the performance may be adversely affected. That is, when the angle 0 becomes su~stantially smaller than 30, the second microphone ~4 receives both the speech and background noise. As a result, upon subtracting the output signal of the second microphone 14 from the output signal of the first microphone 12, a portion or all of the speech may be canceled. On the other hand, when the angle 0 is substantially larger than 60, the background noise received by the second microphone 14 may not be similar to that received by the first microphone 12. As a result, subtracting the output signal of the second microphone 14 from ~he output signal of the ~-first ~icrophone 12 may not adequately cancel the background nois~ received by the first microphone.
In a like ~anner, although th~ angles ~ and ~ have preferred values of less than 359 and approximately 180, respectively, as previously mentioned, the first and second ~5 microphones may op~rate satisfactorily even if arranged so as to OS10:2020,APF~ 12 :, ` ~, :
,: , : .
' "' ` ' ;"
21~9440 PATENT
have different values of these angles. However, as th~ values of ~he angles ~ and ~ become substantially different from the respective preferred values, the performance may be adversely ~ffected. That is, when the angle ~ becomes substantially larger than 35 , the second microphone 14 may receive both the speech and background noise. Similarly, when the angle ~ is substantially smaller or larger than 180, the second microphone 14 may receive both the speech and background noise. As a result, in either of these situations, upon subtracting the output signal of the second microphone 14 from the output signal ~E the first microphone 12, a portion or even all of the speech may be canceled.
As is to be appreciated, by using the above-described ~ ;
devices and materials for the components of the receiver portion 42, the cost for constructing such receiver portion is relatively low. Further, by using CMOS chips, as previously described, the power consumption of the receiver portion is kep~ relatively low.
As a result, the receiver portion may be powered by the standard power available in the handset and, as such, does not require additional power or transformers or the like. Furthermore, although the receiver portion 42 has been described for assembly with the handset 10 of the telephone 8, which is a new telephqne~
such r~ceiver portion, or a slight variation thereof, may be used ln handsets of existing telephones. ~hat is, in this latter situation, the cap and microphone contained within the handset of DglO:2020.APP 1 3 PATENT
an existing telephone are merely replàced with the receiver portion 42. Thus, such use of the receiver portion 42 provides a rolatively easy and low-cost means to modif~ a handset of an ` ~xisting telephone to include the present noise reduction apparatus.
Fig. 4 illustrates a schematic diagram of one circuit arrangement of the telephone 8 shown in Figs. 'L and 2. As shown in Fig. 4, the first microphone 12 is coupled through a resistor -202, which is adapted to function as a current limiting resistor so as to correct the bias of an output ~rom the first microphone, to an input terminal 200. The first microphone 12 is further coupled through a resistor 210 to the plus terminal of the op-amp 16 and through a resistor 212 to a variable resistor 214. The sacond microphone 14 is coupled through a variable resistor 208, which is adapted to function as a current limiting resistor so as to correct the bias of an output of the second microphone, to an input terminal 201, and to the minus terminal of the op-amp 16.
The limiting resistor 208 is preferably a variable current limiting resistor which enables the level of the output signal from the second microphone to be matched to within a predetermined value to the level of the output signal of thP
first ~icrophone 12. More specifically, the limiting resistor 208 enables the output signal of the second microphone 14 to be weighted such that when a signal havin~ a similar level is outputted from the first microphone 12, the amplitude of the DS10:2~.APD 14 .
: , .. .. . ' . ' . ,, ~ ; ~ ' . .' ~
~,109440 PATENT
di~f~irence therebetween is minimized. The value of the current limiting resistor 208 can be selected according to minimization criteria. An input terminal 198 is connected to resistors 204 ~nd 206, which are adapted to divide the voltage received at the ~nput terminal 198, and to the minus terminal of the op-amp 16.
The output of the op-amp 16 is coupled to capacitors 220, 222 and 226 and resistors 224 and 228 which, in turn, is connecte,i to a nmicrophone input" terminal of the telephone unit 18. The output : -:
from the op-amp 16 is further coupled through a variable resistor ~- -214, a resistor 216 and a capacitor 218 to ground. Resistors ~ ~-210, 212 and 216 and variable resistor 214 provide variable gain, ~
.
for example, 20 to 1 amplification, to the output o~' the op-amp 16. 'I'he capacitors 218, 220 and 222 are adapted to remove residual dc (direct current) levels which may be present in the output signal from the op-amp 16. The resistors 224 and 228 and the capacitor 226 are adapted to function as a low-pass filter having a break point at a predetermined value which, for example, may be 3.7 ~Hz.
Th,a t~lephone unit 18 is further connected to the telephone lines and i5 adapted to receive signals through the ~icrophone input ter~inal and to supply these signals to the desired teilephone or telephones by way of the telephone lines.
'The telephone unit 18 is further adapted to receive signals from anothier telephone or telephones by way of the telephone lines and to co~bine such signals with thiose received through the DS10:2020.APP 15 . ~
,`
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Z1~9~4~
PATENT
~ microphone input terminal, as previously described, and to supply .~ ~he combined signal to a speaker input terminal 231. ~he input .~ torminal 231 is connected through a capacitor 230, which is .' ~dapted to block dc signals, and a resistor 232 to the minug terminal of an op-amp 17 and through a resistor 234 to a variable resistor 240. An input terminal 199 is connected to the plus terminal of the op-amp 17. The output from the op-amp 17 is connected through capacitors 242 and 244 and a resistor 246 to the speaker 22. T~e output from the op-amp is further connected through the variable resistor 240, a resistor 238 and a capacitor 236 to ground.
` The operation of the telephone 8 shown in Fig. 4 will now be described below.
Upon activating the handset 10, by lifting the handset ~`;; lS 10 from the switch hook (not shown) or the like, standard telephone line voltage is applied to input terminals 198, 199, ~` 200 and 201. A signal fro~ the first microphone 12, which has ~,i been bias corrected by the current limiting resistor 202, is ~` supplied through the resistor 210 to ~he plus terminal of the op-~` 20 amp 16. An output signal from the second microphone 14, which has ~een bias corrected by the current limiting resistor 208, is ~r supplied to the minus terminal of the op-amp 16. The op-amp 16 ~ubtracts the signal received from the second microphone 14 from that received from the first microphone 12 and outputs the 2S resulting subtracted signal. DC levels which may be present in ~Sl0:2020.API> 16 ' ~-~
. :
st, ~, , . ~ ` -21 0 9 ~ ~ O PATENT
the output signal are removed and the signal is amplified. High ~requency signals, such as those over 3.7 kHz, are then removed -~
fro~ the amplified output signal and the resulting signal is ; upplied to the telephone unit 18. Thus, a voltage signal is ~ -supplied to the telephone unit 18 which is proportional to the difference between the voltages generated by the first and second ~icrophones 12 and 14, respectively.
An output signal from the telephone unit 18, which is a -~
combination of the signals received through the microphone input -~ ~
10 terminal and the telephone lines, is supplied to the input -terminal 231 of the amplifier 20. The signal from the input terminal 231 is supplied to the capacitor 230 so as to remove any dc signals which may be present. The output from the capacitor 230 is supplied through the resistor 232 to the minus terminal of ` 15 the op-amp 17. The op-amp 17 subtracts the signal from the : -telephone unit 18 from the signal received from the input terminal 199 and supplies a subtracted signal therefrom. Such signal may be selectively amplified, through the use o~ resistors ;
232, 234 and 238 and variable resistor 2~0, by the operator by use of the switch 40 (Fig. 1). Any dc signals which may be present in the amplified signal are thereafter removed by the ; capacitors 242, 244 and 236. The output signal from the capacitor 244 is current li~ited by the resistor 24~ and is thereafter supplied to the speaker 22 so as to be converted thereat into an acoustic signal.
DS10:20ZO.APP 17 : ;
- , , , ,. . , . , .. , " . ;, , .
, . . , ~ :
~1~9~
PATENT
Fig. 5 illustrates an alternative arrangement for processlng the signals obtained from the first and second ~$crophones 12 and 14, respectively, so as to provide a current - output for supp}y to the telephone unit 18 which is proportional 5 to the difference of the voltaqes generated by the first and second microphones.
More specifically, the circuit arrangement of Fig. 5 includes a handset 10' having a plurality of input terminals 300, 301, 370 and 390 which are each adapted to receive standard available on-line power. The first microphone 12 is coupled ' through a current limiting resistor 302 to the input terminal 300 and is further coupled to the plus terminal of a subtracting device 316, which is pre~erably a CMOS op-amp. The output from the second microphone 14 is coupled through a variable current limiting resister 308 to the input terminal 301 and is further ~oupled to the minus terminal of the op-amp 316. The signal -outputted from the op-amp 316 is supplied through filtering - stages 350 to the minus terminal of a subtracting device 351 which is preferably a CMOS op-amp. The filtering stages 350 are adapted to provide a predetermined frequency response characteristic such as a signal roll off at a predetermined frequency. As is to be appreciated, although two filtering stages are ~hown in Fig. S any number of ~iltering stages may be utilized. The input terminal 390 is coupled to resistors 392 and , 25 394, which are adapted to reduce the signal supplied thereto, and Dsl0:2020.~PP 18 .` ' , .
. ~
- , , , ; ,: ~, ~ : , , : :
t h 10 9 4 ~1~ PATENT
to the plus terminal of the op-amp 351. An output signal from . the op-amp 351 is supplied to the base of a transistor 366. The input ter~inal 391 is connected to a Zener diode 360, a capacitor . , 362 and a resistor 364 which, in turn, is connçcted to the . S collector of the transistor 366 and to the microphone input terminal of the telephone unit 18. The emitter of the transistor 366 is coupled through resistors 367 and 368 to the minus :~
terminal of the op-amp 351 so as o provide a ~eedback loop ~` thereto. The op-amp 351 and the associated components provide -~
electrical isolation between the filtering stages 350 and the transistor 366. The transistor 366 is adapted to amplify the signal supplied to the telephone unit 18.
~; The output from the telephone unit 18 is coupled to the input terminal 231 ~Fig. 4) and is thereafter processed in the manner previously described with reference to the handset 10 of Fig. 4 so as to provide an acoustic signal from the speaker 22.
The operation of the telephone 8' will now be described b~low.
Upon applying power to the handset 10', by lifting the handset ~rom the switch hook (not shown) or the like, standard ~` telephone line voltage is applied to input terminals 300, 301, ,` 370, 390 and 391. A signal from the first microphone 1~, which ' haQ been bias corrected by the current }imiting resistor 302, is ~upplied to the plus terminal o~ the op-amp 316. An output 25 - oignal from the second microphone 14, which has been bias S DS10:2020.APP 19 :
., .
', ? : . . :
21~9~0 PATENT
corracted by the current limiting resistor 308, is supplied to the minus terminal of the op-amp 316. The resistor 308 i5 pre~erably a variably current limiting resistor which enables the l~vel of the output signal from the second microphone 14 to be matched to within a predetermined value to the level of the ; output signal of the first microphone 12, in a manner substantially similar to that previously described for resistor 208. The output difference signal from the op-amp 316 is provided though the filtering stages 350, which may include one or more RC networks or equivalent circuits, so as to limit the upper frequency of the output signal to a predetermined value which, for example, may be 3.7 kHz. The output signal from the ~iltering stages 350 is supplied to the minus terminal o the op-amp 351 and a voltage signal from the input terminal 390, which ` 15 has been divided to a predetermined value such as one half ` thereof, is supplied to the plus terminal of the op-amp 351 which, in turn, calculates the di~ference therebetween and supplies a corresponding output signal to the base of the transistor 366. The voltage from the input terminal 391 is supplied through the resis~or 364 to ~he collector of the transistor 366. As a result, an amplified signal is supplied from the handset 10' to the telephone unit 18 for supply i t~erefrom through the telephone }ines to the desired telephone(s) nd for combining with a received si~nal from the te}ephone(s) .
DS10:2--0.AW 2 0 ~ .
- ` 21~944~ ~
PATENT
for 8Upply to the input terminal 231 in a manner similar to that previously described with reference to Fig. 4.
The individual circuit components wit:hout reference d~signations depicted in Figs. 4 and 5 are connected as shown and will not be discussed further, since the connec:tions and values ~re apparent to those s~illed in the art and are not necessary ,~ for an understanding of the present invention.
i Figs. 6A, 6~ and 6C illustrate a boom microphone 100 which utilizes a noise cancellation apparatus in accordance with an embodiment of the present invention. More specifically, the boom microphone 100 generally includes a housing 174, a circuit board assembly 178, first and second microphones 112 and 114, respectively, and a portion 147. The housing 174, which may be constructed from either a plastic-like or metal-type material, includes a circular portion 108 having a hole therethrough so as ~,~ to enable a shaft 106 to be inserted therein. As a result, the ` boom microphone 100 may rotate about the shaft 106 as illustrated -` in Fig. 6A.
The first and second microphones 112 and 114 are respectively coupled to the circuit board assembly 178 by wires 102 and 104. Tha circuit board assembly 178 contains circuitry similar to that on the circuit board assembly 78 which, as - previously described, processes the signals from the first and ~econd microphones 12 and 14, respectively, for supply to the telephone unit 18 and, as such, in the interest of brevity, will j~ DslO:20Xl.APP 21 ! ' i;` :
. .' . .
21~9~40 , PATENT
not be further described herein. Therefore, the circuit board aA~embly 178 is adapted to receive a speech and bac~ground noise ~ignal from the first microphone 112 and to subtract therefrom the background noise signal from the second microphone 114 so as to derive a signal which represents substantially the speech.
Such signal is supplied to a transmitting device (not shown) so as to be converted to a RF signal and transmitted to a remote receiving device (not shown). The first and second microphones 112 and 114, respectively, are held in place by a holding member 176 which, for example, ~ay be constructed of a foam-like material. A mesh~ e screen 146 which, for example, may be fabricated from a plastic-type or a metal mat~rial or the like, is attached to the cut away portion 147 so as to protect the ; first and second microphones. The mesh 146 has a predetermined ~ 15 thicknQs~ which, for example, may be approximately 0.030 or less `i, of an inch.
The first and second microphones 112 and 114, respectively, whieh may be electret microphones, are arranged in ~! a ~anner similar to that of the pr~viously described first and .
second microphones 12 and 14, respectively, of the handset 10.
That is, the first and second microphones 112 and 11~, are ~` r~spectively positioned so as to have an angle e~ and [(9o-e~) +
,~ o'~ between a plane parallel to the receiving or sensitive urface of the first ~icrophone and the direction of speech from an operator, and between an axis normal ~o the sensitive surface D510:2020.~PP 22 ?, 9~40 PATENT
of the second microphone and the direction of speech, as shown in Fig. 5A. Further, the first and second microphones 112 and 114, respectively, are arranged so as to have an angle 0' therebetween, which has a preferred value in a range between 30O
and 60. The first and second microphones 112 and 114, respectively, are located in relatively close proximity to the ~esh 146 and the cut away portion 147 of the housing 174 so as not to receive acoustic sounds which have ~een unacceptably distorted.
Although the above embodiments have been described as having only one first microphone 12 (112) and one second microphone 14 (114), the invention is not so limited and any number of microphones may be utilized for the first microphone and/or the second microphone. For example, a receiver portion 42' (not shown) may be configured which includes two or more microphones operating as a first microphone 12' (not shown) and two or ~ore microphones operating as a second microphone 14' (not shown). In this configuration, when using multiple microphones for the first and/or second microphones, respective variable current limiting resistors are preferably provided for all but one micropho~e for the first microphone 12' and for all microphones for th~ second ~icrophone 14'. Thus, the outputs from the first and second microphones, 12' and 14', respectively, would comprise a weighted sum of several such microphone output voltages. The current limiting resistors are preferably set to DS10:2020.APP 23 .
, ~:
:' . .
`` ~109~40 PATENT
respective values so as to minimize some functlonal of the l~ diff~rence of the first and second microphones 12' and 14', respectively. The criterion for selecting the values of the current limiting resistor or equivalently the weighting function Y' of ~ach microphone could be selected according to any well known gradient search algorithm, so as to minimize the functional.
Further, although the above-described embodiments of the present inventisn have been described for use with telephone handsets and boom microphones and the like, the present invention is not so limited and may be used with numerous other devices such as intercom systems and so forth. Additionally, the present 1`
invention ~ay be used with processing devices operating in ,!' accordanc~ with predetermined processing algorithms, as described i`l in U.S. Ratent Application Serial No. 07/887,500 filed May 22, 1992, which has a common assignee with the present application, and which is hereby incorporated by reference.
Furthermore, although preferred embodiments of the present invention and modifications thereof have b~en described in detail herein, it is to be understood that this invention is not limited to those precise embodiments and modifications, and ~ that other modifications and variations may be affected by one i ~killed in the art without departing from he spirit and scope of ~ th~ invention as defined by the appended claims.
.:
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DslO:2020.. ~PP 2 4 ~`
~- ~
,`. , , ...
Claims (33)
1. Noise reduction apparatus comprising:
a housing having first microphone means for receiving a first acoustic sound composed of speech originating from an operator operating said apparatus and background noise, and for converting said first acoustic sound to a first signal, and second microphone means arranged at a predetermined angle ? with respect to said first microphone means for receiving a second acoustic sound composed of substantially said background noise and for converting said second acoustic sound to a second signal;
and means for subtracting said second signal from said first signal so as to obtain a signal representing substantially said speech.
a housing having first microphone means for receiving a first acoustic sound composed of speech originating from an operator operating said apparatus and background noise, and for converting said first acoustic sound to a first signal, and second microphone means arranged at a predetermined angle ? with respect to said first microphone means for receiving a second acoustic sound composed of substantially said background noise and for converting said second acoustic sound to a second signal;
and means for subtracting said second signal from said first signal so as to obtain a signal representing substantially said speech.
2. The noise reduction apparatus according to claim 1, wherein said predetermined angle ? lies within a range from approximately 30 degrees to approximately 60 degrees.
3. The noise reduction apparatus according to claim 2, wherein said first microphone means is arranged in said housing such that an angle ? formed between a plane passing through a portion of said first microphone means which receives said first acoustic sound and an input direction of said speech is less than approximately 35 degrees.
4. The noise reduction apparatus according to claim 3, wherein said second microphone means is arranged in said housing such that an angle .beta. formed between an axis normal to the receiving portion of said second microphone means and said input direction of said speech is approximately equal to [(90 - .theta.) + ?]
degrees.
degrees.
5. The noise reduction apparatus according to claim 1, wherein at least one of said first and second microphone means includes a plurality of microphones.
6. A telephone handset apparatus for use with a telephone unit operable by standard power supplied from said telephone unit for transmitting and receiving signals representing speech between two or more operators, said apparatus comprising:
a housing having first microphone means for receiving a first acoustic sound composed of speech from the operator using said apparatus and background noise in the vicinity of said speech and for converting said first acoustic sound to a first signal, and second microphone means arranged at a predetermined angle ? with respect to said first microphone means for receiving a second acoustic sound composed of substantially said background noise and for converting said second acoustic sound to a second signal; and means for subtracting said second signal from said first signal so as to obtain a signal representing substantially said speech.
a housing having first microphone means for receiving a first acoustic sound composed of speech from the operator using said apparatus and background noise in the vicinity of said speech and for converting said first acoustic sound to a first signal, and second microphone means arranged at a predetermined angle ? with respect to said first microphone means for receiving a second acoustic sound composed of substantially said background noise and for converting said second acoustic sound to a second signal; and means for subtracting said second signal from said first signal so as to obtain a signal representing substantially said speech.
7. The telephone handset apparatus according to claim 6, wherein said predetermined angle ? lies within a range from approximately 30 degrees to approximately 60 degrees.
8. The telephone handset apparatus according to claim 7, wherein said first microphone means is arranged in said housing such that an angle e formed between a plane passing through a portion of said first microphone means which receives said first acoustic sound and an input direction of said speech is less than approximately 35 degrees.
9. The telephone handset apparatus according to claim 8, wherein said second microphone means is arranged in said housing such that an angle .beta. formed between an axis normal to the receiving portion of said second microphone means and said input direction of said speech is approximately equal to [(90 - .theta.) + ?]
degrees.
degrees.
10. The telephone handset apparatus recording to claim 6, wherein at least one of said first and second microphone means includes a plurality of microphones.
11. The telephone handset apparatus according to claim 6, further comprising amplifier means for selectively amplifying a signal received from one or more of said operators so as to produce an amplified signal therefrom.
12. The telephone handset apparatus according to claim 11, wherein said first and second microphone means, said means for subtracting and said amplifier means are powered by said standard power supplied from said telephone unit.
13. The telephone handset apparatus according to claim 12, wherein said means for subtracting and said amplifier means are formed on a low-powered integrated circuit chip.
14. The telephone handset apparatus according to claim 13, wherein said low-powered integrated circuit chip is a Complementary Metal Oxide Semi-conductor (CMOS) chip.
15. The telephone handset apparatus according to claim 8, further comprising protecting means for protecting said housing, said protecting means including a portion having a predetermined thickness and a number of holes contained therein and which is situated adjacent to said first microphone means.
16. The telephone handset apparatus according to claim 15, wherein said predetermined thickness is less than approximately 0.030 of an inch.
17. The telephone handset apparatus according to claim 15, wherein said protecting means further includes a side portion and wherein said portion having said predetermined thickness is located below an upper portion of said side portion.
18. The telephone handset apparatus according to claim 17, wherein said protecting means is formed from a plastic-type material.
19. Apparatus for use with a telephone handset for reducing acoustical noise, said apparatus comprising:
a housing having first microphone means for receiving a first acoustic sound composed of speech from an operator using said telephone handset and background noise in the vicinity of said speech and for converting said first acoustic sound to a first signal, and second microphone means arranged at a predetermined angle ? with respect to said first microphone means for receiving a second acoustic sound composed of substantially said background noise and for converting said second acoustic sound to a second signal; and means for subtracting said second signal from said first signal so as to obtain a signal representing substantially said speech.
a housing having first microphone means for receiving a first acoustic sound composed of speech from an operator using said telephone handset and background noise in the vicinity of said speech and for converting said first acoustic sound to a first signal, and second microphone means arranged at a predetermined angle ? with respect to said first microphone means for receiving a second acoustic sound composed of substantially said background noise and for converting said second acoustic sound to a second signal; and means for subtracting said second signal from said first signal so as to obtain a signal representing substantially said speech.
20. The apparatus according to claim 19, wherein said predetermined angle ? lies within a range from approximately 30 degrees to approximately 60 degrees.
21. The apparatus according to claim 20, wherein said first microphone means is arranged in said housing such that an angle .theta. formed between a plane passing through a portion of said first microphone means which receives said first acoustic sound and an input direction of said speech is less than approximately 35 degrees.
22. The apparatus according to claim 21, wherein said second microphone means is arranged in said housing such that an angle .beta. formed between an axis normal to the receiving portion of said second microphone means and said input direction of said speech is approximately equal to [(90 - .theta.) + ?] degrees.
23. The apparatus according to claim 19, wherein at least one of said first and second microphone means includes a plurality of microphones.
24. The apparatus according to claim 19, further comprising amplifier means for selectively amplifying a signal received from another operator so as to produce an amplified signal therefrom.
25. The apparatus according to claim 24, wherein said first and second microphone means, said means for subtracting and said amplifier means are powered by standard power supplied to said telephone handset.
26. The apparatus according to claim 25, wherein said means for subtracting and said amplifier means are formed on a low-powered integrated circuit chip.
27. The apparatus according to claim 26, wherein said low-powered integrated circuit chip is a Complementary Metal Oxide Semi-conductor (CMOS) chip.
28. The apparatus according to claim 25, further comprising protecting means for protecting said housing, said protecting means including a portion having a predetermined thickness and a number of holes contained therein and which is situated adjacent to said first microphone means.
29. The apparatus according to claim 28, wherein said predetermined thickness is less than approximately 0.030 of an inch.
30. The apparatus according to claim 28, wherein said protecting means further includes a side portion and wherein said portion having said predetermined thickness is located below an upper portion of said side portion.
31. The apparatus according to claim 30, wherein said protecting means is formed from a plastic-type material.
32. The noise reduction apparatus according to claim 1, wherein the first and/or second microphone means comprises a plurality of microphones and outputs from the first and/or second microphone means comprises a weighted sum of several microphone output voltages which are weighted according to a desired function.
33. The noise reduction apparatus according to claim 32, wherein the desired function is a gradient search algorithm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/968,180 | 1992-10-29 | ||
| US07/968,180 US5381473A (en) | 1992-10-29 | 1992-10-29 | Noise cancellation apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2109440A1 true CA2109440A1 (en) | 1994-04-30 |
Family
ID=25513863
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002109440A Abandoned CA2109440A1 (en) | 1992-10-29 | 1993-10-28 | Noise cancellation apparatus |
Country Status (11)
| Country | Link |
|---|---|
| US (1) | US5381473A (en) |
| EP (1) | EP0595457A1 (en) |
| JP (2) | JPH06224987A (en) |
| KR (1) | KR0158465B1 (en) |
| CN (2) | CN1041042C (en) |
| BR (1) | BR9304419A (en) |
| CA (1) | CA2109440A1 (en) |
| IL (1) | IL106984A (en) |
| MX (1) | MX9306601A (en) |
| MY (1) | MY109919A (en) |
| TW (1) | TW371547U (en) |
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-
1992
- 1992-10-29 US US07/968,180 patent/US5381473A/en not_active Expired - Lifetime
-
1993
- 1993-09-10 IL IL10698493A patent/IL106984A/en not_active IP Right Cessation
- 1993-09-16 EP EP93307336A patent/EP0595457A1/en not_active Withdrawn
- 1993-09-20 MY MYPI93001902A patent/MY109919A/en unknown
- 1993-10-25 KR KR1019930022175A patent/KR0158465B1/en not_active IP Right Cessation
- 1993-10-25 MX MX9306601A patent/MX9306601A/en not_active IP Right Cessation
- 1993-10-27 TW TW086216422U patent/TW371547U/en unknown
- 1993-10-27 JP JP5268776A patent/JPH06224987A/en active Pending
- 1993-10-28 CA CA002109440A patent/CA2109440A1/en not_active Abandoned
- 1993-10-29 BR BR9304419A patent/BR9304419A/en not_active Application Discontinuation
- 1993-10-29 CN CN93119803A patent/CN1041042C/en not_active Expired - Fee Related
-
1997
- 1997-07-05 CN CN97114556A patent/CN1183018A/en active Pending
-
1998
- 1998-02-27 JP JP000970U patent/JPH10228U/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH10228U (en) | 1998-09-29 |
| CN1041042C (en) | 1998-12-02 |
| IL106984A0 (en) | 1993-12-28 |
| CN1183018A (en) | 1998-05-27 |
| MX9306601A (en) | 1994-04-29 |
| CN1096621A (en) | 1994-12-21 |
| KR940010604A (en) | 1994-05-26 |
| IL106984A (en) | 1997-02-18 |
| MY109919A (en) | 1997-09-30 |
| KR0158465B1 (en) | 1998-12-01 |
| TW371547U (en) | 1999-10-01 |
| US5381473A (en) | 1995-01-10 |
| JPH06224987A (en) | 1994-08-12 |
| BR9304419A (en) | 1994-05-03 |
| EP0595457A1 (en) | 1994-05-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |