Патент USA US2121778код для вставки
June 28, 1938. 4 . s. BALLANTINE , 2,121,778 SOUND TRANSLATÍNG APPARATUS ‘ Filed Feb. 12, 1935 . 2 Sheets-Sheet / / / /00 /0000 1 June 28, 1938. _ l s. BALLANTINE 2,121,778 SOUND TRANSLATING APPARATUS Filed Feb- 12, 1955 2 Sheets-Sheet- 2 Patented June 28, 1938Y I l Il ‘ Y ' l ’ UNITED STATES PATENT OFFICE ~ ‘ « n - " A'2,121,228 t , .SOUND TRANSLATING APPARATUS Stuart Ballantine, Mountain Lakes, N.Í I. u Application February 12, 1935, sci-iai Nc. 6,245 ' 14 omme- (ci. 11s-1) This invention relates to sound translating ap- _ . essary for intelligible transmission in a, tele-Ä. paratus and particularly 'to sound translating ' phone circuit, since these are the principal com. » apparatusadapted for incorporation in an elec- .-‘stituents Yof the majority of consonants. _ _ trical communication system. 5 ` . ' - Iv have discovered that the higher speech fre The ordinary ktypes of microphones, designed to be actuated by aerial sound waves, must be supported in front of, and preferably. close to, quencies are represented, in appreciable magni- 5_ tudes, in the vibratory energy available at the larynx, and that the frequency-vibration ampli " ,the mouth. There are many applications and, tude characteristic is such that a high degree of uses for microphones, however, where this is quite naturalness in the reproduced sound may be ob-» A 1o 'inconvenient . even in those cases where somel tained by restoring the balance in the frequency 101 means of support, other ythan the hands, are distribution oi energy. Broadly speaking, this is . provided. Examples of such use areY in gas and accomplished by designing the pickup device and oxygen masks. -According to this invention, I `its associated apparatus' to be much more einabandon the method of picking up the sound cient at high frequencies than at low frequen .lll5 from the air and instead pick up the sound as cles, or in other Words, to have a, rising fre- 15> it exists in the vibration oí ,the upper parts of quency response characteristic. . the body which are set up by the acoustical and . ‘Objects of the invention are to provide novel mechanical actions of 'the voice. These vibra- methods and apparatus for converting into elec tions are particuia'riy >strong ini-,he region of the . trical currents, for transmission over an electri ' 20 larynx and associatedV cartilaginous structures cal system, the acoustical vibrations of certain 20. such as the thyroid cartilage. Devices embody- Darts 0f the body. Objects are t0 provide meth ing the invention include apparatus that is ap- ods of and apparatus for producing electrical plied to the vibrating parts so as to be directly R currents from mechanical vibrations of the actuated by the mechanical vibrations thereof ‘£25 and 'acoustical transmission through the air plays -a minor role. ’ throat, the electrical currents being such that, when converted back to sound, the sound re- g5 ì production will closely resemble the original voice Throat microphones have been proposed but, - of the person as heard in the ordinary way or so far as I know, none .of the prior devices has as picked up by a microphone of conventional been successful in yielding an electrical output 3o which was a faithful replica of the'natural sound „ of the voice. The sound reproduced by the 'prior devices was composed largely of low frequency components and was muilled,rdeep and booming, type designed for aerial sound `waves.' A further object is to provide apparatus for. 3th use in an electrical communication system, the. apparatus being designed for actuation by me chanical vibrations of the throat and being capa being so highly unintelligible as to be totally un` 35 ñt for electrical communication purposes. , ble of producing electrical currents> which are comparable with the currents produced by a good 36; I have made an experimental study. by wave microphone when favorably positioned for actu analysis, of the mechanical vibration amplitudes ation by the voice or sound waves in air.> More of the larynx at different .frequencies and have particularly, an object is to provide a mechano-` found the reason for the failure of the prior electrical transducer adapted to be placed in con-z . 40.V devices. I,_have found that the vibration am- tact with and actuated by the mechanical vibra.. ‘i0~` Plítlldes 0f the larynx' diminish Very> rapidly as , tions of the body and a. transmission network co the frequency ' increases and, COHSeCillently, the operating with the transducer to deliver electrical- . priorart devices did not yield intelligible sounds, Waves ,évmßh’ when impressed u'pon a telephone - for the devices were designed Simply t0 reproduce ‘45 the vibrations as they exist with total disregard oi their spectral distribution.` . _ . _ This frequency distribution of the vibratory. line or other electrical communication system, , result .in a reproduction of sound that has the. acoustical quality of the voice. T] _ ' energy is reconcuable with the fact that many invenîzsiîirîlnwdïilcl'tllxi‘îer ggîîaîrïânîngrîïlîhïgfîhgîwîä; the sounds of speech,involving highupper fre 50 of quency constituents, are formed in the cavitiesthebylarynx, the lips andattenuated, tongue and reach much by probably a back- ward acoustical' transmission which may be more aerial than mechanica. It is wcii established . specification when taken with the accompanying litiÉ drawings, in which: F15 11S a curve sheet ShÜW-lng 9' frequency-Ye' spons@ 'Óhm'actel'istïc Which Will Yield highly ar“, ticulated Speech from the mechanical ’fibratìßnß 55 that these higher frequency components are nec-A ot the larynx; ‘. . 2,121,778 Fig. 2 is a circuit diagram of a sound reproduc ' ing system which embodies the invention; Fig. 3 is a curve sheet showing the frequency response characteristicspf the Fig. 2 apparatus; Fig. 4 is a fragmentary circuit diagram of an other embodiment of the invention; ' Fig. 5 is a curve sheet showing the frequency response characteristics of the microphone and of the complete system of Fig. 4; and _ _ 10 detail in my copending United States application Ser. No. 6,246, filed concurrently herewith. From a broad point of view, the desired fre quency characteristic shown in Fig. 1 applies to the entire system, including the device used to translate the electrical current back` to sound. This frequency characteristic may be divided be tween several elements of the system as may be v„found economical or expedient. It may be, for Fig. 6 is a fragmentary circuit diagram illus trating a modification of the Fig. 4 circuit. example, incorporated solely in the microphone, 10 or partly in other apparatus. It will usually be I have determined, from my studies of the re advantageous to obtain the frequency character lation between frequency and the vibration ampli istic as near to the microphone as possible, in tudes of the larynx, that there is a general pro 15 gressive decrease in amplitude towards the higher end of the useful voice frequencies of from- 200 to about 4,000 cycles and have determined em pirically a. frequency response characteristic which may be employed with satisfactory results 20 to correct for the non-uniform energy input at different frequencies. The frequency response order to avoid the necessity of altering existing circuits into which the apparatus is to work. 15 A representative embodiment of this invention is shown in Fig. 2. -This represents a complete telephone system of a simple type. Here the microphone I comprises a carbon-granule cell of conventional type which is provided with a button 20 2 which is driven by the vibration of the larynx. characteristic of the apparatus can be described, _ The microphone output is fedinto the network for explanation of this invention and for engi neer-ing purposes, by means of a curve showing 25 the output voltage of the system when the micro-` phone is vibrated mechanically by a piston which is driven sinusoidally at constant velocity at all frequencies. The term “constant velocity" means that the maximum value of the velocity 30 (which varies sinusoidally) is maintained con stant. This method of defining the frequency characteristic has been adopted in view of the difñculty of actuating the microphone over the entire frequency range for measurement pur 35 poses when it is worn on Vthe throat. -The me then through transformer T1, the line, and trans former T2 to the telephone receiver 3. 'I'he con 25 denser Ca serves to confine the direct current from battery 4 to the microphone circuit. The desired frequency characteristic, shown in Fig. 1, is obtained by means of the network in combi nation with the mechano-electrical character 30 istic of the microphone. If the microphone is so designed as to have a constant output for a given displacement at all frequencies, its output voltage, for constant velocity excitation, will vary inversely as the first power of the frequency as 35 shown by curve B, Fig. 3. The network provides chanically driven piston is used merely as a con venient way of imparting a definite and repro ducible actuation to the microphone. Lilla, RiRz, C1C2 of the constant resistance type, ' The frequency response or transmission char 40 acteristic shown by curve A of Fig. 1 has been the rising transmission characteristic, curve C, and these transmission characteristics combine to provide the required characteristic, curve D. 'I‘he apparatus shown to the left of line ab of found, experimentally, to -yield highly articulated speech from the mechanical vibration of the Fig. 2 may‘be replaced by the equipment illus larynx. The ordinates represent the Velectrical _ trated in Fig. 4. The device I’ which converts voltage output while the abscissae indicate the the vibrations of the larynx into electrical voltages includes two imite 4 that are applied 45 corresponding frequencies at which the micro symmetrically to the larynx and which, as shown, 45 phone was vibrated, as explained above, by a con stant velocity piston. To obtain this constant are of the piezoelectric type .such as described in my copending application. The units are wired velocity, the amplitude of vibration varied in versely as the frequency. As shown by the dotted >in parallelso that their effects are additive elec 50 line A', the output of the pickup system varies as trically, and are shielded electrically by the the 1.3 power of the frequency over the greater metallic housing 5 and shielded cord 6, one ter 50 Dari. of the curve A. It willv be seen from this minal of `each piezoelectric unit being grounded curve that a considerable readjustment of the ' to the shield. . » The output terminals of the microphone are relation between high and low frequencies is re connected to the input terminals of the iirst tube 55 quired to compensate for the frequency distribu Ation in the larynx. It must be understood, of ‘i of a two-stage amplifier. These input terminals 55 course, that the shape and slope of the curve is are shunted by a resistance R1 which serves as a not critical, but may be varied somewhat from grid leak to fix the direct current bias on thethat shown in Fig. 1. The diagram is intended _ grid G1 of tube 1 and which has the further 00 to show the order of the effect and to indicate function of establishing a definite relation be _why a device of conventional design (for uniform tween the alternating current voltage applied to 60 response at all frequencies) is doomed to failure. the grid and the voltage generated by the micro It must also be pointed out that the anatomical phone, the relation being such that the input and other variations between individuals and of . voltage rises with frequency. A part of the de the position of the microphone _on the throat sired frequency characteristic of the whole system would make a closer specification of a desirable may thus be obtained at this portion of the cir 65 cuit. This eiïect is obtained by selecting a value characteristic of doubtful practical value. The microphone should respond over as great for resistance R1 which is lower than the capaci a frequency range as possible, but it has been tive reactance of the piezoelectric crystals in the microphone at the higher frequencies. A rela70 found in practice _that good telephone communi tively low value of resistance R1 has other ad 70 cation can be obtained by the inclusion ci' fre quencies up to from 3000 to 5000 cycles. 'I'he vantages in that it tends to minimize any varia curve in Fig. 1 represents the performance of an . tion in output due to leakage in the microphone actual apparatus including a microphone of the- crystals or the connecting cord. The relation between the voltage across re piezoelectric type as described below and in more sistance R1 and the voltage generated by the 75 2,121,778 microphone in a typical dotted line curve E of Fig. 5. It will be understood that there is considerable case is shown by the l latitude in the choice or design of the different_ The various fre elements of the sound translating apparatus, and `quency components of the electrical currents in the frequency response characteristics of the were generated from the mechanical- vibrations of the body at- conversion ratios that increased several elements. The desired frequency response characteristic of the complete system may be ob with frequency in the useful voice frequency range. The conditions under which this curve tained in a variety of ways other than those here was obtained were as follows: the two crystals the resistor R1 could be made larger and the re sulting reduction in the power of the response 10 versus frequency relation can be compensated in connected in parallel each had a capacity of I.001 v microfarad atV 20° C., and resistance R1 was 50,000 ohms. . in described. In the Fig. 4 circuit, for example, the design of the microphone or the amplifier. The rising frequency characteristic of the It will therefore be apparent that the invention is not restricted to the particular methods and amplifier, principally the first stage, to have a. embodiments herein described and that various rising frequency characteristic, i. e. a gain _that changes which will occur to those familiar with rises with frequency. `The plate circuit of the >this art fall within ,the scope of my invention' pentode tube 1 of this stage includes the primary as set forth in the following claims. ' microphone is supplemented by designing the ' winding of the coupling transformer T1 in paral lel with a resistance Rs, the reactance of the transformer being low compared with the resist ance R3 and plate resistance in parallel, thus providing a gain characteristic which rises with frequency. The transformer T1 is in fact made I claim: 1. Sound translatingapparatus comprising a 20 mechano-electric transducer substantially non responsive to sound waves in air and actuated by the vibrations of the body due to the voice, and an electrical network for transmitting the elec resonant at a frequency near the upper limit of f trical output of said transducer, said transducer 25 the desired frequency range. The frequency and network having an overall frequency re characteristic of the second stage, tube 8; is sub sponse characteristic which rises progressively stantially flat.' By shunting the output trans with frequency from 200 to about 4000 cycles former T2 th a resistance R5, the output im when the transducer is vibrated at constant veloc pedance, viewed from the output terminals, may ity, whereby the electrical current output of said be made a substantially pure resistance at all network may be converted into sound waves hav« frequencies. In this way, the microphone and ing an acoustical quality comparable to that of associated amplifier may be adapted to replace _ the -conventional carbon¿microphone of about the2. voice.. Sound translating apparatus as claimed in 100 to 200 ohms resistance without aifecting the claim 1, wherein said transducer has a frequency 35 frequency characteristics of other parts of the responseLcharacteristic which falls off with in 35 creasing frequency, and said network has a char - circuit. To limit regeneration, the terminals of trans acteristic which rises with frequency at a rate former T1, as shown, are >reversed from their normal polarity. Grid biases for vthe two amplifier which ‘ overcompensates the falling vcharacter 40 of said transducer. tubes are obtained from the voltage drop through istic 3. Sound translating apparatus as claimed in 40 and R4, respectively. v the cathode resistances R2, claim l, wherein both said transducer and said The condensers C1, C2, C3 are the usual by-pass network have frequency response characteristics condensers to limit intercircuit coupling, resist which rise with frequency. y ‘ ances ReRi are decoupling resistances in the plate 4. Sound translating apparatus comprising a 4.5v circuits, and resistance Ra is a so-called bleeder. mechano-electric transducer susbtantially non 45 The overall >frequency characteristic of the responsive to sound waves in air and actuated'by amplifleris‘shown by the curve F of Fig. 5 in the vibrations of the body due to the voice, and which the ordinates represent the output voltage an electrical network for transmitting the elec- ~ plotted against frequency for a fixed voltage trical output of said transducer, said transducer 50 applied across the resistance R1. The relation and network having an overall frequency response 50 between the voltage output terminals of the characteristic which rises as a predetermined amplifier andfrequency, for a constant velocity power of the frequency over the voice frequency excitation of the microphone, is shown by curve rangev of from 200 to about 4000 cycles when the transducer is vibrated at constant velocity, 55 A of Fig. 1. It is not always convenient mechanically to whereby the electrical current output of said net-and in such work may be converted into sound waves having completely shield~ the-'microphone of the micrephone is in an acoustical quality comparable to that of the cases, when the wearer a radio frequency radiation iield, some radio fre quency energy may leak to the amplifier. Ex voice. m5,.,-Sound translating apparatus comprising a 60 60 amples of such situations are found in open cock A_a'rfi'echano-electric transducer substantially non pit airplanes where the microphone may be used responsive to sound waves in air and actuated by to modulate a radio transmitter. Such stratl " the vibrations of the body due to the voice, and radio frequency voltages may be prevented from an electrical network for transmitting the elec. reaching the grid of the amplifier tube by a filter 65 network. such as shown in Fig. 6. The general form of the ampliñer circuit may be substantially identical with that shown in Fig. 4, and certain elements of the Fig. 6 circuit are therefore identi trical output of said transducer; said transducer and network having an overall frequency response characteristic which rises ças'V a power of the fre» 65 quency which is not lessithan unity over the use-» ful voice frequency ,range of from 200 to about 4000 cycles when-the transducer is vibrated at 70 The filter circuit for blocking the ‘ _constant velocity, whereby the electrical current transmission of radio frequency voltages com output of said network may be converted into prises the choke coil L and the shunt condenser sound waves having an acoustical quality ,com C which are connected between the microphone parable to that of the voice. ' ' system com 75. terminals and the input terminals of the ampli fled by the corresponding‘reference characters 70 of Fig. 4. 6. 'An electrical communication 75 fier. ` 4» 2,121,778 >prising a mechano-electrical transducer substan tially non-responsive to sound waves in air and actuated_ by the mechanical vibrations of the body due to voice, a transmission circuit, and a sound reproducer, said system having an overall transmission eiiiciency which produces an output generated by the microphone which rises with frequency. .10. In sound translating apparatus, the com~bination with a throat microphone including a. transducer unit, and a. vacuum tube amplifier stage having output terminals; of means for that rises progressively with frequency in the developing across the output terminals of said useful voice frequency range of from 200 to amplifier stage an output voltage which rises about 4000 cycles when the transducer is vibrated , with frequency when said microphone is vi 10 at constant velocity, whereby the reproduced brated at constant velocity, said means including sound has an vacoustical value simulating that of an. additional amplifier stage between said mi the voice. crophone and said first-mentioned amplifier 7. An electrical communication system of the stage, the additional amplifier stage having a type including'a mechano-electrical transducer 15 substantially non-responsive to sound waves in air and actuated by mechanical vibration of the body due to the voice, a transmission circuit, and a sound reproducer, characterized by the fact rising frequency characteristic. 11. 'I‘he invention, as claimed 'in claim 10, wherein the additional amplifier stage includes a transformer resonating at a frequency near the upper limit of the range of frequencies vto that the system has an output which rises as a be transmitted thereby. 20 power of the frequency over a substantial part of ` 12. The invention as claimed in claim 10, in the useful voice frequency range of the system- combination with a ñlter network between said of from 200 to about 4000 cycles when the trans ducer is vibrated at constant velocity, whereby the reproduced sound has the acoustical quality 25 of the voice. 8. In sound translating apparatus, combi nation with a throat microphone of the piezo electric type, said microphone having a capacitive reactance over its frequency range of response, of 30 a resistor shunted across the output terminals of said microphone, the resistorhaving a resistance less than the capacitive reactance offs'aid micro phone over the greater part of the said frequency range of response, whereby the relation between the output voltage across the microphone termi microphone and the additional'amplifier stage to prevent the application of radio frequency voltages to the additional amplifier stage. 13. 'I‘he process of reproducing speech which comprises the steps of translating mechanical vibrations of the body due to the voice into elec- c trical currents, selectively amplifying the several frequency components of the vibration-produc d currents at gains which increase with the frê quency of such components in the useful voi `e frequency range of.i’rom 200 to about 4000 cycles, 30 transmitting the amplified electrical currents tò a. desired reproduction point, and converting the transmitted and amplified currents into sound 35 nals and voltage generated by the microphone Waves. , rises with frequency. 14. 'I'he process of reproducing speech which 9. In sound translating apparatus, the combi f includes the steps of selectively generating elec nation with a throat microphone of the piezo trical currents from mechanical vibrations of the 40 electric type, said microphone having a capaci--. body due to the Voice at conversion ratios that 40 tive reactance over its frequency range of re increase progressively with frequency in the use spouse, a resistance shunted across the output terminals of the microphone, a vacuum tube and connections between the input terminals thereof and the microphone terminals, and an impedance network cooperating with said tube to effect oper ation thereof as an amplifier, `the overall trans mission emciency of said microphone and ampli ñer varying with frequency to produce a relation between 4amplifier output voltage and -the voltage ful voice range ‘of from about 200 to about 4000 cycles, amplifying the resulting electrical currents at gains which increase progressively with fre quency within the said useful voice range, trans mitting the amplified electrical currents, and converting the transmitted and amplified cur rents into sound waves. i STUART BALLANTINE.