ANTI-FEEDBACK, FULL-DUPLEX HEADSET
BACKGROUND OF THE INVENTION
The present invention relates to methods and apparatus for reducing feedback of headsets in which the speaker and the microphone are both located adjacent the user's ear.
In the past, a number of methods have been devised for reducing the acoustic feedback that can occur when microphones and speakers are located near each other. One method is to use a half-duplex communication system. In a half- duplex communication system, acoustic feedback is avoided since the microphone is not operating to pick-up sound during the time period in which the speakers operate. Half-duplex communications, however, may be unacceptably limiting for some uses, such as telephone communication and multimedia.
Another method used in the past to avoid acoustic feedback is the use of ear canal occlusion. By physically blocking the user's ear canal either by covering it or by using a plug inserted into the opened ear canal, acoustic feedback can be prevented while sounds can still be delivered within the canal. Standard communication headsets and hearing aids both fall within this category. This approach works well, but has the disadvantages of being somewhat uncomfortable and can prevent the wearer from clearly hearing ambient sounds. Additionally when the ear is plugged, one's own voice does not sound normal.
Another method of avoiding acoustic feedback is to design a physical separation between the sound delivery and sound pick-up transceiver. One example in this category is a boom microphone, which places the microphone near the mouth. This approach is used in the familiar telephone headset and other devices. This approach also works well, but previous devices using this approach
place limits on how small the entire acoustical device can be, which limits the discreetness and convenience of the device.
It is desired to have an improved method of avoiding acoustical feedback in a small and discrete system in which a microphone and speaker are located adjacent to users' ear.
SUMMARY
The present invention comprises a system having two elements, both of the elements having a speaker and at least one of the elements having a microphone. These elements can be two parts of a headset or two separate earpieces. Both of the speakers are used for a listening-only mode. For a two-way communication mode the speaker in the element with the microphone is turned off and that microphone is used for voice pick-up while the speaker at the opposite ear element provides the received communication audio. Thus, in the two-way communication mode there is a physical separation and head-shadowing to prevent feedback. Switching into this mode can be automatically or manually controlled.
In an alternate embodiment of the present invention, the output of the speaker adjacent to the microphone can be reduced, in order to prevent feedback. In an additional embodiment, one of the speakers can receive a filtered signal where the other speaker on the side of the head opposite to the microphone receives an unfiltered signal.
The present invention allows isolation between sound delivery and sound pick-up transceiver to prevent feedback during the two-way communication mode. The present invention also allows for normal hearing with unoccluded ears while still providing full duplex operation. The system of the present invention allows a
binaural headset used in entertainment devices and multimedia to switch into a two-way communication mode when the need arises for voice pick-up.
In an alternate embodiment of the present invention both elements have microphones. Both microphones can be used to provide normal sound pick-up in a half-duplex mode. For full-duplex communication operations, one microphone is switched off and the receiver at that earpiece is switched on. If both earpieces have microphones, the system can determine which earpiece is at the quietest location and use that information as a factor to determine which microphone to use for sound pick-up in order to optimize voice pick-up quality. In an additional embodiment, when alarm, call progress, or other tones are used, the microphone/receiver switching does not have to occur across the entire audio band, but can be done at certain portions of the band or at specific frequencies. For example, output of the microphone adjacent to the speaker, can be filtered in a notch filter to remove the tones transmitted by the speaker, yet still allow normal voice pick-up.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagram illustrating an example of a system that can be used for the present invention.
Figure 2 is a block diagram that illustrates an example of a system that can be used with the present invention.
Figure 3 is a flow chart that illustrates the operation of one embodiment of the present invention.
Figure 4 is a flow chart that illustrates alternate methods of operation the second mode of the present invention. Figure 5 is a flow chart illustrating an alternate embodiment of the present invention.
Figure 6-8 are diagrams of earpieces that can be used with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 is a diagram that illustrates an apparatus that can be used with the present invention. The apparatus 20 includes elements 22 and 24. The elements 22 and 24 each have a speaker 24a and 22a and a microphone 24b and 22b. The elements 24 and 22 can be part of a headset, as shown in figure 1 , or could be two separate earpieces. In the preferred embodiment, the elements 22 and 24 are arranged so that they do not completely occlude the ear canal of the user. Details of a communication system with a microphone and speakers which do not completely occlude the user's ear canal described in the U.S. Patent applications WIRED OPEN EAR CANAL EARPIECE, Serial No. 08/833,064, filed April 3, 1997 and WIRELESS OPEN EAR CANAL EARPIECE, Serial No. 08/833,068, filed April 3, 1997, which are both incorporated herein by reference. When the speaker and microphone are both positioned at an element adjacent to user's ear, and the ear canal is not occluded, problems with acoustic feedback can exist. A method to avoid this problem of acoustic feedback is described below.
Figure 1 shows an embodiment in which the remote unit 26 has a wireless connection to the elements 22 and 24. This connection could alternately be wired. Figure 2 is a block diagram that illustrates an apparatus 30 which is useful for operating the method of the present invention. The apparatus 30 includes elements 32, 34, and a remote unit 36. The remote unit 36, in the preferred embodiment, is attached to receive a binaural audio signal on line 38. The
binaural signal can be a monaural signal sent to both ears or a stereo signal. Examples of binaural audio signals include audio signals used in entertainment programs or multimedia. Line 40 shows a two-way connection which is sent to the remote unit 36. The two-way connection may be a telephone connection. Alternately, both the binaural signals and the two-way signals can be part of an interactive computer environment. The system of the present invention can switch between two modes. The switching can be controlled automatically (for example upon detecting the user's voice) or manually. The first mode transmits binaural audio data from line 38 to speakers in both elements. In the second mode, full- duplex communication, such as a telephone link across line 40, occurs. The remote unit 36 includes processing circuitry 42 for receiving and transmitting signal from the binaural audio line 38 and telephone line 40. The processing circuitry 42 converts this data into the proper format for transmitting with the transmitter /receiver 44. For example, the processing circuitry 42 can packetize the data and add overhead information for transmitting of data. The processing circuitry can also depacketize the data received from the elements 32 and 34. The transmitted data is sent to transmitter/receivers 46 and 48 in the elements 32 and 34. The transmitter/receivers 46 and 48 send the data to the processing circuits 50 and 52 in the element 32 and 34. The processing circuits 50 and 52 can determine whether transmitted data is addressed to that element and convert correctly addressed transmitted data into an output for the speakers 54 or 56.
In the preferred embodiment, each element has a speaker. At least one of the elements 32 or 34 include a microphone. In figure 2, element 32 contains the microphone 58. Optionally, an additional microphone 60 could be contained within the element 34. The advantages of positioning the microphone 58 at the same location as the speaker 54, is that it allows for a compact earpiece unit. The microphone 58 sends the detected audio signal to the processing circuitry 50.
The processing circuitry 50 converts the detected signal into digital data to be transmitted to the remote unit 36.
As described below, when the binaural audio data is received on line 38, the processing circuitry 42 can digitize the data and add the overhead information, including the address for the elements 32 and 34. The digital data is transmitted from transmitter/receiver 44 to the transmitters/receivers 46 and 48 in the elements 32 and 34. The data is sent to the processing circuitry 50 and 52 which sends the properly addressed data to the speakers 54 and 56, so that a binaural signal can be received. When a telephone signal or some other signal which requires full-duplex communication is received, the processing circuitry 42 interrupts the transmission of the binaural audio data from line 38. In this embodiment, the audio data received from telephone line 40 is converted to audio data transmitted from the transmitter/receiver 44 to the element 34. The processing circuit 52 converts the data into the audio data to be sent to speaker 56. No audio data is transmitted to speaker 54, which is in effect turned off. The data from the microphone 58 can be processed and sent to the remote unit 36 so that the processing unit 42 can transmit the voice pick-up along telephone line 40. Acoustic feedback is prevented because the sound from speaker 56 is shadowed by the head and prevented from being detected at a significant level by microphone 58 at element 32 on the other side of the head. After the telephone call is finished, the binaural signals are again sent to both speakers 54 and 56.
It is also possible for the processing circuitry 42 to produce control signals which can be interpreted by the processing circuitry 50 or 52 at the elements 32 and 34 in order to turn off the speaker or microphone as desired. In one embodiment, another microphone 60, positioned in element 34, is used. The processing circuitry 42 can select the microphone which produces the best quality voice pick-up. The speaker adjacent to the selected microphone is then turned off.
In an alternate embodiment, the processing circuit 42 could merely reduce the output of a speaker 54 in some way other than turning the speaker off when a call is received. This could be done by filtering the speaker signal sent through the processing circuitry 42 or by merely reducing the amplitude of the speaker 54. In another embodiment of the present invention, if dial tones or alarms are transmitted, the processing circuit 42, or alternately processing circuits 50 or 52, can filter the detected signal from the microphones 58 or 60 in order to remove the frequencies at this tone. This can be done easily by a digital signal processor acting as notch filter to remove the specific tones from the signal transmitted on line 40.
Additional details of communication systems that can be used with present invention are given in the patent applications, EAR CANAL MICROPHONE, Serial No. 08/832,507, filed April 3, 1997, and OPEN CANAL HEARING DEVICE, Serial No. 08/781 ,714, filed January 10, 1997, which are incorporated herein by reference .
Figure 3-5 are diagrams that illustrate the operation of the present invention. Figure 3 is a flow chart that illustrates the switching between the modes. In the first mode, step 80, binaural audio signals are sent to both speakers 54 and 56 in elements 32 and 34. If a telephone call is received, then the system switches to the second mode, step 82. In the second mode, the microphone 58 is on and the output of the speaker adjacent to the microphone 58 is reduced. When the telephone call is over, the system returns to the first mode in step 80. Figure 4 show details of the second mode operation 82' . In one embodiment, 82a when the microphone 58 is on, the speaker 54 adjacent the microphone 58 is turned off. The speaker 54 can be turned off either by no longer sending audio data from the remote unit 36, or by sending a control signal which turns off the speaker 54. Alternately, in step 82b, the microphone 58 can be turned on while the signal to the speaker 54 adjacent to the microphone 58 can be filtered. This filtering can be
done by the processing circuitry 42 or in an alternate embodiment by the processing circuitry 50.
Figure 5 is a flow chart for another embodiment for the present invention. In this system, in step 90, both of the speakers are on. In step 92, the microphone 58 is turned on for full-duplex communication. The speaker 54 at the location with the microphone 58 produces an output within a certain range of frequencies. This could be an alarm tone sent to both speakers 54 and 56. In step 94, the output of the microphone 58 is filtered to remove the range of frequencies of the tones sent to the speaker 54. In this way the microphone signal sent through the telephone line 40 does not contain the alarm tones. This can be done by digital filtering within the processing circuit 42 or 50. The processing circuit 42 or 50 will determine the frequency range to be transmitted through the speaker 54 and then filter the output of the microphone 58 accordingly.
Figure 6-8 illustrate embodiments of earpiece units that can be used with the present invention. Figure 6 shows an earpiece 100 with microphone 102 and speaker 104. Figure 7 shows an embodiment with a microphone 108 positioned in above the ear and a speaker 110 that sits over the entrance to the ear canal. A clip 112 can be used to hold the earpiece on the ear. Figure 8 shows an earpiece 114 with a microphone 116 and the tube 118 to carry sound to the ear canal. The tube 118 is relatively small so that the ear will not be completely occluded.
A variety of other earpieces could be used with the present invention. It will be appreciated by those of ordinary skill in the art, that the present invention can be embodied in other specific forms without departing from the spirit or essential character thereof. The present disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is illustrated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range for equivalence thereof are intended to be embraced herein.