US2415215A - Stroboscopic tuning apparatus - Google Patents

Description

J. H. 'MAYBERRY STROBOSCOPIC TUNING APPARATUS Filed Jan. 5, 1944 glu/verdon J. ff. MA1/BERRY www0 Feb. 4, 1947.

Patented Feb. 4, v1947 'UNITEDITSTATES PATENT Vor `s'rltolsoscorrc TUNmG APPARATUS .lohn H. Mayberry, Corpus Christi,K Tex. Application January 5, 1944, Serial No. 517145 (o1. :is-14) 2 Claims.

This .invention `relates to limprovements in stroboscopic tuning apparatus and pertains particularly to apparatus of this character designed for visual tuning. f

In some present known types yof stroboscopes use ismade of gears for drivingv or turning the rotating members. the use of gears, to drive the usual discs which areemployed each for a particulartone, to ob-A tain speed ratios between the discs` of thesame value as the ratios between 'the numbers of vibrations in the successive chromatic notes. As is correctly stated vin prior Patent No. 2,286,030 an exact ratio cannotv be secured by the use of gears andvarious means have 4been devised for compensating this ydeficiency but with all such meansr there still remains, because of the use of the gears as stated in the patent referred ltopa margin oferror. v

The present invention has for avprimary ob- Jectvthe provision of a stroboscopic tuning apparatus designed primarily for tuning musical instruments, although it is not limited to such use, wherein the use of gears is entirely avoided and whereby the ratios between the rotating visual elements or indicators are absolutely the same in the successive chromatic tones.

Another object of the invention is to provide an improved stroboscopic apparatusA which makes possible the measuring of frequencies which come out in fractions. l n

Still another,A object of the invention isto provide an improved stroboscopic tuning apparatus making use of a single rotating member which carries a plurality ofgroups of symbols representing tone ing a direct ratio to' a known pitch frequency,

as the ratios ybetween the numbers yof vibrations frequency or pitch values each havy However it is not possible, by i with a synchronous motor operating means for turning' the member at a known speed whereby the correctness of tone of any one of.' the numberr of tones'of lknown pitch value covered by such groups will be shown upon causing theiiashing frequency of an `illuminating lamp to be varied overthe range of the frequencies `of the tones represented by the said groups.

Still another object of the invention is to `provideran improved stroboscopic apparatusof the character above set forth in which the series of values carried Iby the rotating member is graduated to cover the pitch of tones over an entire octave and in which the member is rotated at synchronousspeed for coaction with a asher controlled by electric current vibrationshaving frequencies corresponding to sound vibrations.

a conventional manner withV an Another object of the invention is to provide a stroboscopic apparatus of the characterabove stated, by means vof which a change `I,in speed will change the'v pitch offthe fentire in which, also, it is possibleV to tune several octaves without changing thev 'speed of rotation yof the turning member or by which the pitch may be raised a.frafzticnfof a` tone `or to a suillcient'vdegree' to place the entire pattern of the tone value indicating symbols on the Vrotating member, in a diierent octave by changingv the synchronous'speed of the rotating member.

Many other ladvantages and objects ofy the present invention will become apparent as the description of the same proceeds, and the invention will 'be best understood from a consideration of the following detailed description taken in connection with ,the accompanying' drawing forming a part of the specification, it being -understood that minor changes and modiiications may be made in the invention so long asvsuch changes and modifications mark no material de-v parture from the salient features of the invention as expressed lin the appended claims.

In the drawing: y d Figure` 1 is a diagrammatic illustration of a stroboscopic apparatus constructed'in accordance with the present invention.

Figure 2 illustrates conventionally a form of synchronous ymotor forming a part of the cylinder structure. f

Figure 3 is a diagram illustrating the application of the invention to a vibrator.

Figure 4 illustrates a form of casing Ior housing in which the apparatus may be inclosed ior use.

In accordance with the form of a microphone I0, which is coupled in apparatus l l of any conventional design. Y

The out-'put of the amplifier is fed into a neon or gas discharge tube lI2 through an impedance matching transformer. Accordingly as will be readily recognized the apparatus translates sound vibrations into electric current vibrations having corresponding frequency and the glow lamp or tube l2 will be energized by said current vibra-l tions at the same frequencies as those of the sound vibrations picked up bythe microphone I0.

The stroboscopic member of the present ap-` octave and the present invention, an s illustrative embodiment of whichy is diagram-` matically shown inthe accompanying drawing there is-provided a sound pick-up instrument in audiofamplifying pali'atus is in the form of a cylinder I3 which is horizontally disposed and rotatablysupported at-its ends, in any suitable manner for rotation Y.

about its longitudinal axis. The cylinder forms 'ana integral part of and Ais turned by a synchroto the .pickup and amplifying system as illus-l 'trated.

While there has been shown and described a` lsynchronous motor turning at two and a half revolutions per second, there may be employed a motor turning at any other synchronous speed such as 3.157 R. P.-S., which construction would, Y

. of course, require 38 poles instead of 24 as previously stated for'the rst-mentioned speed.

AThe cylinder I3 has formed around the surface' I2 encircling series of dots, squares or other suit'- able symbols which make up a black and white pattern corresponding to l2 tones in a chromatic. octave, the octave selected for use being that below middle C on a key-board instrument.

While itis not essential to the use of the inl t vention that the cylinder be inclosedin a housing, such housing is, however, illustrated and designated I 6, with the slot window I 1 through which may be viewed the series of circular linesof symbols carried bythe cylinder. The Provision., of

such a housing also makes convenient the placement of the values I8 each above anddesignating the number of dots or symbols in each of the lcircular lines or series,4

' Below the window and in the line with values I8 maybe placed the conventional tone symbols I9 of Athe selected octave with the frequency values thereof as/i'ndicated at 20.

The whole `tones such, for example, as A1220,

will have an even number of dotsor symbols in l C-261.62, are arranged to spiral around thecyl-v inder insuch a way as to make at least three complete rcircles of the cylinder as `indicated at 2 I. The series of dots above referredto asdesignating the tone A, is designated 22. Y Y

The values indicated at I8 above the window give the number of symbols in each circular series forming a fraction of the frequencyv values for the under-lying indicated tones. When the` cylinder is turned by the synchronous motor at the selected speed and the lamp I2 is flashed at the correct frequency of a particular tone, such as A, for example, the flashes of the lamp and the movement of the dots each past one point willk be synchronized yso that the dots or symbols of the series A will appear to be stationary thereby showing the toneto be at the proper pitch or spiral series 2 I, the dots are in such number and arrangement that in one revolution of the cylinder 104.65 dots will pass the point of observation and upon turning of the cylinder two and a half measuring of frequencies which come outy in fractions. Since in any key-board instrument it is necessary to set a temperament in order to play Yin many keys without using anv inconveniently large number o keys to the octave, the temperament, which it vis necessary to set. on these instruments determines the degree of departure from the pure scale in order to accomplish this. This is also the reason why the tones come out in fractions. As previously pointed out the use of gears in a device of the character herein described to obtain a separate vpattern for each tone, is not `possible since the mathematical ratio available with the use of gears will not give the required separation.

The separation of the tones inany key-board `instrument graduates at the ratio of the twelfth root of two, or in other words Aa ratio of 1.05946. This separation cannot be obtained by the use of gears in the rotation of patterns as set forth y above but it is possible for the rotation of they patterns by the means herein disclosed.

In further illustration of how the desired sep-l aration orratio between the patterns is obtained to correspond to the separation between the frequencies of the tones of the chromaticscalathe illustration in Figure 1 makes clear how, on a basis of 2.5 revolutions per second for the cylinder the frequencies noted are available, which frequencies cover the octave below C, universal pitch of A-440. If the cylinder is revolved at two times this speed, or five revolutions per second, the next higher octave will be available, begin-` ning with C sharp-277.18.

The observed pattern remains in'tune within of the present invention, the musical tone isiirst Y picked up by the microphone I0 and amplified by the audio-amplifier unit II. The output of the amplifier unit is fed into the tube I2, which may be a neon or any suitable tube, thus illuminating the revolving' pattern. Since the eye cannot separate pulsations of light above 26 per second, the light will appear to be steady.

The pattern is being turned at a denite rate of speed with the black and white lines passing the point of observation corresponding to the tones of the chromatic tempered musical scale. For example, the tone of A-220 C. P. S. is sounded and at the same time the A zone of the revolving pattern is observed. There are 220 black lines per second passing the point of observation. If thev tone is in tune, a black line will be at the same place every time the light flashes, or every 1,220 of a second, therefore, the zone will appear stationary.

I1', for example, the tone was 219 C. P. S., the black lines or dots would continue to pass at 220 lines per second andthe light would be flashing only 219 times per second. Thus the line, or dot, will appear at a slightly different place each time and will move the interval of one line per second in the direction of the pattern rotation or movement. If, however, the tone was 221 C. P. S., the line or dot would appear' to recede, or move back, from the direction of pattern rotation.

In the case of fractional tones, such, for vexample, as the tone of D293.67, the intervalbetween the lines or dotswill allow one line or dot to pass the point of observation every 1/293.67 of a second. Since in any stroboscopic apparatus resonance is denoted by the apparent stability of the zone, the interval between all lines or dots on the component or zone of the pattern must be the same, just as the time interval between flashes of light must be the same for the particular frequency under observation. Spiral components or zones were designed for the tones of fractional frequency with the correct interval between lines or dots corresponding to the tone of fractional frequency. In observing the pattern i-t is not necessary to follow one turn of the spiral, but to observe all of the zone as a whole since all ofthe lines or dots of the zone are equally spaced. Resonance is denoted in the usual manner, that is, by the apparent stability of the zone.

The 412 semitones or half-tones of the octave of the chromatic tempered scale are therefore designed for the ratio of the 12th root of 2 or a graduation of 1.05946 per semitone, the single pattern with 12 zones or components of the pattern corresponding to the frequency of the tones of the standard octave when tempered.

The pitch could be changed, however, changing the speed of rotation.-

Figure 3 illustrates a method of tuning a vibrator with the use of an ignition coil 24, the vibrator being designated 23. The neon tube is connected across the secondary of the ignition coil while the primary of the coilA is connected across the vibrator points for excitation. A resistance 25 of twenty thousand ohms is placed in series with the secondary of the coil and the neon or gas discharge tube. to avoid over-load.

The present device is selective and discriminates between noise and a musical tone. It is possible for one to teli at a glance whether a tone is sharp or at. If the tone is in tune or in resonance the pattern will remain stationary but it it is sharp the `dots will move upward, and if it is ilat the dots will move downward. When the `tone is adjusted so that the pattern remains stationary, the tone will be in resonance or in unison with the revolving pattern.

The technique ofthe instrument is mechanically perfect since the pattern remains ilxed and the established ratio of vibration for each tone is xed. Operation of the device at a higher or lower speed will change the pitch of the entire octave but at the same time alltones within the rotating pattern bear a linear relationship between each other. If the speed is doubled, for instance, the octave higher can be tuned as previously pointed out.

It is also possible to tune several octaves without changing the speed, however the patterns will appear diferently. For example the octave above will make the dots appear to be twice in number and there will also be a shift in the position. The octave below will look much, like the fundamental octave but not so sharp. An instrument can b tuned to any pitch by changing the to thus eliminatethe use of governors or various means of imparting the desired speed to the cylinder. K

The -pitch may be raised a fraction of a tone or it may be raised enough to place the entire pattern in a different octave. For example, turning the cylinder at 3.157 revolutions per second which is a synchronous speed, will give the octave F to E around middle C in the pitch orali-441.1. It will be noted that the even number of dots previouslyused for F sharp, as illustrated in Figure 1 now becomes A sharp-233.70 which is a fraction. 'I'his is an example of the flexibility of the apparatus. Any desired pitch can be obtained by changing the speed of rotation oi' the cylinder.

Two tones can also .be sounded simultaneously and the respective patterns will be observed on the device at the same time, since the frequencies will be different and the observer may easily note two symbol groups simultaneously, each of which would represent a tone and be illuminated at the tone frequency.

While in the preceding description reference has been made entirely to the tuning of musical instruments it is to be understood that lthere is no intention of limiting the scope of the invention to such use since it may be used to-tune any piece of apparatus producing an audible sound such as mechanical vibrators and automobile horns, or for measuring the speed of rotating objects, calibrating oscillators, and checking tachometers.

I claim:

1. A stroboscopic apparatus, comprising a body supported for rotation, a number of groups of symbols carried by such body, the symbols o! each group being disposed around and substantially concentric with the axis of rotation of the body, each group representing a tone of the musical scale, the symbols representing the tones of even frequency being arranged in a circle and the symbols representing tones oi' fractional frequency being arranged to form a spiral, each of said groups consisting of a whole number of identical symbols, the symbols of each group being equally spaced apart so that the same number of symbols passes a point of observation with each revolution of the body, means for turning the body on said axis at an unvarying number oi' revolutions per second, which number of revo'- lutions multiplied by the number of symbols passing the point of observation per revolution is the exact frequency `of the musical tone represented .by each group of symbols, means for translating sound vibrations into electric current vibrations having corresponding frequencies, and a glow lamp arranged to illuminate the body and the groups of symbols and connected with the sound translating means to be energized by the electric current vibrations at the said frequencies.

2. A stroboscopic apparatus, comprising a body supported for rotation, a group of symbols on said body and arranged around and substantially concentric with the axis of rotation of the body, the group consisting of a whole number of identical symbols, said group representing a musical tone of fractional frequency and lbeing arranged in a spiral, the symbols of the group being equally spaced apart, so that the same nu'mber of symbols passes a point of observation with each revolution of the body, means for turning the body on said axis at an unvarying number of revolutions per second, which number of revolutions multiplied by the number of symbols passing the point of observation per revolution is the exact frequency of the musical tone represented by the group, means for translating sound vibrations into electric current vibrations having corre- 5 sponding frequencies, and a glow lamp arranged to illuminate the body and groups of symbols and connected with the sound translating means to be energized by the electric currentl vibrations at the said frequencies,

JOHN H. MAYBERRY.

REFERENCES CITED `Ihe following references are of record in the le of this patent:

Number UNITED STATES PATENTS Name Date Kriek June 7, 1938l Young et a1 June 9, 1942 Elton Sept. 22l 1942 Dodd Nov. 25, 1919

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