US2288839A - Sound translating device - Google Patents

Description

July 7, 1942. c, pyE 2,288,839

SOUND TRANSLATING DEVICE Filed NOV. 2'7, 1959 5 Sheacfi Shefit 1 INVENTOR ATTORNEYS July 7, 1942. H. c. PYE' SOUND TRANSLATING DEVICE Filed Nov. 27, 1939 3 Sheets-Sheet 2 INVENTORQ Harold C Pye BY ATTORNEYS July 7, 1942.

, H. C. PYE

SOUND TRANSLATING'DEVICE 3 Sheets-Sheet 3 Filed Nov. 27, 1939 .QBm SQ I motmb wk Patented July 7, 1942 NT OFFICE SOUND TRANSLATING DEVICE Harold C. Pye, Oak Park, Ill., assignor to Associated Electric Laboratories, Inc., Chicago, 111., a

corporation of Delaware Application November 27, 1939, Serial No. 306,287

4 Claims. (Cl. 179-122) The present invention relates to sound translating devices and more particularly'to telephone transmitters.

A conventional telephone transmitter is responsive to sound waves of different frequencies disposed within the audible frequency range and including background sound waves having frequencies disposed within a first band in the audible range and signal ound waves having frequencies disposed within a second band in the audible range. Ordinarily, the background sounds or noises have frequencies disposed toward the lower end of the audible range; 'while the signal sounds have frequencies disposed toward the higher end of the audible range. Consequently, the telephone transmitter transmits sou: 0. energy corresponding both to the background noises and to the signal sounds; thereby to cause a telephone receiver associated with the telephone transmitter to reproduce both the background noises and the signal sounds.

Accordingly, it is an object of the present invention to provide a telephone transmitter embodying an improved arrangement for preventing the transmitter from transmitting sound energy corresponding to the background noises.

Another object of the invention is to provide in a transmitter, an improved mechanical filter arrangement for filtering out undesirable noises having frequencies disposed within a predetermined frequency band in the audible frequency range of the transmitter.

Another object of the invention is to provide in a sound translating device having a predetermined inherent acoustical response over a given frequency range, an improved mechanical filter arrangement for altering the effective acoustical response of the device over a given frequency band within the given frequency range.

A further object of the invention is to provide a sound translating device which is of extremely simple and rugged construction, which is compact and economical to manufacture and which is efficient in operation.

In general, the objects set forth above are in part realized in accordance with the present invcntion by p oviding a sound translating device in the form of a telephone transmitter which comprises a substantially cup-shaped casing, a

vibratory diaphragm, means for securing the being resiliently connected to the casing and movable with respect thereto, and a movable mechanical system coupled to the second electrode. During the operation of the transmitter the vibratory diaphragm is subjected to sound waves having different frequencies in the audible range including background sound waves having frequencies disposed in a first band in the audible range and signal sound waves to be transmitted having frequencies disposed in a second band in the audible range, whereby the sound energy transmitted by the transmitter corresponds to the relative movement between the electrodes, the movable mechanical system constitutes means for filtering out the background sound energy. More particularly, the mechanical system comprises mass and stillness characteristics which are so proportioned and related that the second electrode is moved with the first electrode when the diaphragm is subjected to the sound waves having frequencies disposed in the first band i the audible range.

Two modifications of the movable mechanical system are disclosed. In accordance with one modification, the movable mechanical system is commonly coupled to the first and second elec trodes, whereby the relative movement between the first and second electrodes is controlled, the system being arranged in the casing and including a number of mass rings and a numberof connecting stiffness rings constructed and arranged to provide a bellows construction extending between the first and second electrodes. In accordance with the other modification, the movable mechanical system is commonly coupled to the second electrode and the casing, whereby the relative movement between the second electrode and the casing is controlled, the system being arranged in the casing and including a number of mass rings and a number of stiffness rings constructed and arranged to provide a bellows construction extending between the second electrode and the casing.

More particularly the transmitter comprises an impedance element in the form of a charge of carbon granules disposed between the first and second electrodes, whereby relative movement between the first and second electrodes is effective to control the effective impedance of the impedance element such that the variation in effective impedance of the impedance element corresponds to sound energy to be transmitted by the transmitter.

Further, it is noted that the transmitter has a predetermined inherent acoustical response over the audible frequency range and that the movable mechanical system constitutes a mechanical filter for establishing a cut-off point disposed Within the audible range, whereby the effective acoustical response of the device is a substantially negligible value on one side of the cut-off point and an appreciable value on the other side of the cut-off point, wherein the location of the cut-off point within the audible range is determined by both the mass and stiffness characteristics of the system. Finally, it is noted that the effective acoustical response of the transmitter is a substantially negligible value on the side of the cut-off point disposed toward the low frequency end of the audible range and an appreciable value on the side of the cut-off point disposed toward the high frequency end of the audible range, whereby the transmitter is effective to transmit sound energy corresponding only to relatively high frequency signal sounds.

Further features of the invention pertain to the particular construction and arrangement of the elements of the sound translating device, whereby the above-outlined and additional op erating features are attained.

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, together with further objects and ad.- vantages thereof, will best be understood by reference to the following specification taken in connection with theaccompanying drawings, in which Figure 1 is a plan view of one form of sound translating device embodying the present invention; Fig. 2 is a longitudinal sectional view of the device taken along the line 2-2 in Fig. 1; Fig. 3 is a plan view of a modified form of sound translating device embodying the present invention; Fig. 4 is a longitudinal sectional view of the device taken along the line 4-4 in Fig. 3; and Fig. 5 is a graphic illustration of the performance characteristics of sound translating devices of the types illustrated in Figs. 1. 2 and 3, 4.

Referring now more particularly to Figs. 1 and 2 of the drawings, there is illustrated a preferred embodiment of a sound translatin device in the form of a telephone transmitter H) which comprises a substantially cup-shaped housing H including a flat bottom wall l2, a central dome l3, a cylindrical side wall M, an annular flange l5 and a cylindrical side wall IS. the flange l5 bein disposed between the side walls l4 and I6. Prefably, the housing H is formed of a suitable aluminum alloy in order to obtain a rigid lightweight mounting for the elements of the transmitter and supports a suitable mouthpiece, not shown. An annular face plate I! is arranged within the sidewall N5 of the housing II and retained in place by an annular flange l8 spun from the side wall l6 into enga ement with the face plate Preferably the face plate I! is formed of a suitable aluminum alloy and is provided with a number of openings |9 therein arranged in a circular pattern in ord r to permit sound waves to enter the housing H. An annular groove 20 is provided in the cylindrical side wall of the face plate I! in order to provide a resilient gripping action between the side wall of the face plate I1 and the side wall 56 of the housing II when the annular flange I8 is spun from the side wall l6 into engagement with the face plate H.

The housing ll encloses a moving a thin cushioning ring 28 formed of insulating material is disposed between the flange 25 carried by the primary diaphragm 2| and the annular shoulder 21 provided on the face plate l1. Finally the front wall of the primary diaphragm 2| is covered with a moisture-proof protective covering 29.

The casing element 23 comprises a substantially central dome 30 and a wide annular flange 3|. Finally the secondary diaphragm 22 comprises an annular ring disposed between .the annular flange 25 carried by the primary diaphragm 2| and the annular flange 3| carried by the easing element 23; the inner periphery of the secondary diaphragm 22 being suitably secured to the annular flange 3| and the outer periphery of the secondary diaphragm 22 being suitably secured to the annular flange 25. The center of the dome 24 carried by the primary diaphragm 2| is secured to the center of the dome 30 carried by the casing element 23 by an eyelet or rivet 32,- thus forming a composite diaphragm assembly which is very stiff over the central conical portion and extremely flexible over the outer edge flange portion. Also it is noted that the eyelet 32 has an opening 33 provided therein in order to provide a breathing action between the interior of the casing element 23 and the outside atmosphere. Also, the telephone transmitter I0 comprises a casing element 34 includ-*- ing a substantially central dome 35 and a wide annular flange 36, the dome 35 carried by the casing element 34 being arranged within the of thin duralumin sheet metal in order to obtain the combination of light weight parts having high tensile strength.

A ring-shaped electrode 38 is suitably secured to the annular flange 3| carried by the casing element 23 adjacent the dome 30 thereof; similarly,

a ring-shaped electrode 39 is' suitably secured to the annular flange 36 carried by the casing element 34 adjacent the dome 35 thereof. Preferably, the electrodes 38 and 39 are formed of solid carbon and are sealed with respect to each other by an annular corrugated flexible paper bellows 40 extending therebetwe'enand cemented thereto. Further it is noted that a charge of carbon granules. not shown, is arranged within the domes 30 and 35 of the casing elements 23 and 34, respectively, and extends between the electrodes 38 and 39, the interior surfaces of the domes 39 and 35 respectively carried by the casing elements 23 and 34 being varnished in order to electrically insulate the casing elements 23 and 34 from the charge of carbon granules disposed spectively secured to the annular flanges 3| and 38 respectively carried by the casing elements 23 and 34; while theinsulating rings 44 and 45 are respectively secured between the metallic rings 4|, 42 and 42, 43, thereby to provide a bellows construction surrounding the electrodes 33 and 39 and extending between the annular flanges 3| and 36.

The bottom wall l2 of the housing carries an electrical terminal 46 electrically connected thereto and an electrical terminal 41 electrically insulated therefrom, the terminal 41 being electrically connected by a flexible conductor 48 to a plug 49 carried by the dome 35 of the casing element 34. Accordingly the terminal 49, the housing II, the primary diaphragm 2|, the casing element 23 and the electrode 38 are arranged in series circuit relation; while the terminal 41, the conductor 48, the plug 49 the casing element 34 and the electrode 39 are arranged inseries circuit relation, the charge of carbon granules being disposed between the electrodes 38 and 39.

During the operation of the telephone transmitter the charge of carbon granules disposed between the electrodes 38 and 39 is variably compressed in accordance with the relative movements between the electrodes 38 and 39, thereby to vary the electrical impedance or resistance of the circuit extending between the terminals 48 and 41.

Also during operation of the telephone transmitter Ill, movement of the primary diaphragm 2 I, and consequently movement of the casing element 23, is damped by the action of a resonance chamber 58 formed between the primary diaphragm 2| and the face plate l1; movement of the casing element 34 is damped by the resilient bellows 31; while movement of the casing element 23 with respect to the casing element 34 is damped by the resilient bellows 40 and bythe breathing action of the air passing through the opening 33 formed in the eyelet 32 incident to movement of the casing elements 23 and 34 with respect to each other.

Finally it is noted that the movements of the casing elements 23 and 34 with respect to each other, and consequently the movements of the electrodes 38 and 39 with respect to each other, are controlled by the mechanical low-pass filter arrangement disposed between the annular flanges 3| and respectively carried by the casing elements23 and 34.

More particularly, at lowfrequencies, the mechanical low-pass filter arrangement constitutes in effect a substantially rigid connection between the annular flanges 3| and 36 respectively carried by the casing elements 23 and 34, thereby to cause the movements of the casing elements 23 to be transmitted directly to the casing element 34. Accordingly, at low frequencies, the electrodes 38 and 39 are not moved substantially with respect to each other. Hence the mechanical lowpass filter arrangement prevents low frequency sound energy from being transmitted from the telephone transmitter or filters out low frequency sound energy. On the other hand, at high frequencies, the mechanical low-pass filter arrangement constitutes in effect no connection between the annular flanges 3| and 38 respectively carried by the casing elements 23 and 34, thereby to cause the casing element 23 to move with respect to the casing element 34. Accordingly, at high frequencies, the electrodes 38 and 39 are moved substantially with respect to each other. Hence the mechanical low-pass filter arrangement does not prevent high frequency sound energy from being transmitted from the telephone transmitter or permits high frequency sound energy to pass.

.From the above description of the mode of operation of the mechanical low-pass filter arrangement commonly associated with the casing elements 23 and 34 it will be understood that the telephone transmitter is effective to transmit at substantial magnitudes only sound energy having a frequency disposed above a given cut-off frequency.

Further it will be understood that the point of cut-off of the telephone transmitter i may be controlled by varying the mass of the metallic rings 4|, 42 and 43 and by varying the stiffness of the insulating rings 44 and 45. More particularly, by increasing the stiffness of the insulating rings 44 and 45 or.by decreasing the mass of the metallic rings 4|, 42 and 43, the point of cut-off of the telephone transmitter l0 may be shifted from a given frequency band to a higher frequency band; on the other hand, by decreasing the stiffness of the insulating rings 44 and 45 or by increasing the mass of the metallic rings 4|, 42-and 43, the point of cut-off of the telephone transmitter I! may be shifted from a given frequency band to a lower frequency band. Further it will be understood that any reasonable number of insulating rings and metallic rings may be provided in the telephone transmitter l0, and that the number of insulating rings and metallicrings provided will not alone control the point of cut-off of the telephone transmitter l9, as the point of cut-off of the telephone transmitter will be determined by the ratio between the composite mass of the metallic rings and the composite stiffness of the insulating rings.

The construction and arrangement of the sound translating device shown in Figs. 1 and 2 are disclosed. and claimed in the copending-divisional application of Harold C. Pye, Serial No. 413,184, filed October 1, 1941.

Referring now more particularly to Figs. 3 and 4 of the drawings there is illustrated a modified embodiment of a sound translating device in the form of a telephone transmitter of the same general construction and arrangement as the telehpone transmitter l8, previously described. More particularly, the telephone transmitter 68 comprises a housing 6| including a flat bottom wall 92, a cylindrical side wall 63, an annular fiange G4 and a cylindrical side wall 65, the flange 84 being disposed between the side walls 83 and 85. Further the telephone transmitter 69 comprises a face plate 86', a diaphragm assembly 61'. two casing elements 88 and S9 and two electrodes 19 and T1 constructed and ar ranged in the general manner previously explained. Further it is noted that the casing element 88, includes a centrally disposed dome 12 and a'narrow annular flange 13; while the casing element 89 includes a centrally disposed dome 14 and a wide annular flange 15, the electrodes 19 and 1| being respectively secured to the annular flanges 13 and 15 respectively carried by the casing elements 68 and 69 adjacent the domes thereof, and an annular corrugated resilient paper bellows 16 being cemented to the electrodes 70 and II.

In the telephone transmitter 60 a mechanical lcw-pass filter arrangement ,is commonly associated with the casing element 69 and the bottom wall 62 of the housing 6| which comprises fivemetallic rings ll; l8, i9, 80 and 8!, four rings of insulating material 82, 83,-84 and 85 and a metallic disk 86. More particularly, the metallic disk 86-is rigidly secured-toan electrical terminal 8'! carried by the bottom wall 62 of the housing 6| and electrically insulated therefrom; while the metallic rings TI and 8| are respectively secured to the flange carried by the casing element 69 and the disk 86. The insulating rings 62 and 85 are respectively secured to the metallic rings and 8| and to the metallic rings 76 and Bil; while the insulating rings 33 and M are respectively secured to the metallic rings 78, it and i9, 80. Finally an annular corrugated flexible paper bellows 86 is arranged between the insulating ring 85 and the disk 86.

Also the bottom wall 62 of the housing 6! carries an electrical terminal 89 electrically con,- nected thereto; while the electrical terminal 8] is electrically connected to a plug 90 carried by the casing element tit by a flexible conductor 6!. Hence, the terminal 39 is electrically connected by way of the housing M, the diaphragm assembly 6i and the casing element 68 to the electrode Vii; while the terminal 87 is electrically connected by way of the conductor M, the plug 90 and the casing element $8 to the electrode "ii, a charge of carbon granules being disposed between the electrodes m and H.

During operation of the telephone transmitter 68 movement of the diaphragm assembly 611, and consequently movement of the casing element 68, is damped by the action of a resonance chamber 92 formed between the diaphragm assembly 61 and the face plate @6; movement of the casing element 69 is damped by the resilient bellows 88; while movement of the casing element 68 with respect to the casing element 69 is clamped by the resilient bellows I6 and by the breathing action of the air passing through the opening formed in the eyelet incident to movement of the casing elements 68 and 69 with respect to each other.

Finally it is noted that the movements of the casing element 69 with respect to the bottom wall 62 of the housing 6i, and consequently the move-.

ments of the casing elements 68 and 69 and the electrodes 16 and it with respect to each other, are controlled by the mechanical low-pass filter arrangement disposed between the housing element 69 and the bottom wall 62 of the housing 6|.-

sound energy from being transmitted from the telephone transmitter or filters out low frequency sound energy. G n the other hand, at high 1* quencies, the mechanical low-pass filter at ment constitutes a rigid connection between the annular flange 15 carried by the casing element 69 and the disk 86, thereby to prevent movement of the casing element 69 with respect to the bottom wall 62 of the housing 6| and to cause movement of the casing element 68 with respect to the casing element 69. Accordingly, at high frequencies, the electrodes 10 and H are moved substantially with respect to each other. Hence,

the mechanical low-pass filter arrangement does.

not, prevent high frequency sound energy from being transmitted from the telephone transmitter or permits high frequency sound energy to pass.

From the above description of the mode of operation of the mechanical low-pass filter arrangement commonly associated with the casing element 69 and the bottom wall 62 ofthe housing 6 I, it will be understood that the telephone transmitter is effective to transmit at substantial magnitudes only sound energy having a frequency disposed above a given cut-oif frequency.

Further, it will be understood that the point of cut-off of the telephone transmitter 60 may be controlled by varying the mass of the metallic rings 11, 18, 19, and 8| and by varying the stiffness of the insulating rings 82,63, 84 and 85. More particularly, by decreasing the stiffness of the insulating rings 82, 83, 84 and 85 or by decreasing the mass of the metallic rings 71, i8, 19, 80 and 8!, the point of cut-oil of the telephone transmitter 60 may be shifted from a given frequency band to a higher frequency band; on the other hand, by increasing the stiifness of the insulating rings 82, 83, B4 and 85 or by increasing the mass of the metallic rings 11, 18, i9, 80 and BI, the point of cut-off of the telephone transmitter 60 may be shifted from a given frequency band to a lower frequency band. Further it will be understood that any reasonable number of insulating rings and metallic rings may be provided in the telephone transmitter 60, and that the number of insulating rings and metallic rings provided will not alone control the point of cutoff of the telephone transmitter 60, as the point of cut-off of the telephone transmitter will be determined by the product of the composite mass of the metallic rings and the composite stiffness of the insulating rings.

Referring now to Fig. 5 there is illustrated graphically .two performance curves A and B of two telephone transmittersA and B having either the general construction of the telephone transmitter II] or the general construction of the telephone transmitter 60. It is noted that the telephone transmitter A has a cut-off point occurring between 300 and 400 cycles per second; thereby to cause the telephone transmitter A to transmit a current variation corresponding to a low sound output of the order of minus 8 decibels or below in the frequency band below 300 cycles per second, and to transmit a current variation corresponding to a high sound output of the order of plus 8 decibels or abovein the frequency band above 400 cycles per second. On the other hand, the telephone transmitter 13 has a cut-off point occurring between 700 and 800 cycles per second; thereby to cause the telephone transmitter B to transmit a current variation corresponding to a low sound output of the order of 0 decibels or below in the frequency band below 700 cycles per second, and to .transmit a current variation corresponding to a high sound output of the order of plus 7 decibels or above in the frequency band above 800 cycles per second.

A telephone transmitter of the general con struction of the telephone transmitter l0 and having a performance curve corresponding to the performance curve A may be altered to have a performance curve corresponding to the performance curve B by appropriately increasing the stiiiness of the insulating rings or by appropriately decreasing the mass of the metallic rings, in the manner previously explained. Similarly, a telephone transmitter of the general construction of the telephone transmitter 60 and having a performance curve corresponding to the performance curve A may be altered to have a performance curve corresponding to the performance curve B by appropriately decreasing the stiffness of the insulating rings or by appropriately decreasing the mass of the metallic rings, in the manner previously explained.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is contemplated to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A telephone transmitter comprising a substantially cup-shaped casing, a vibratory diaphragm, means for securing said diaphragm adjacent the peripheral edge thereof in the open end of said casing, first and second electrodes arranged in said casing, said first electrode being rigidly connected to said diaphragm and movable therewith, said second electrode being resiliently connected to said first electrode and movable freely with respect thereto, a movable mechanical system arranged in said casing and including a plurality of spaced-apart mass rings and a plurality of interposed stiffness rings connected together to form a compact bellows-like structure extending between and coupled to said second electrode and said casing, whereby the relative movement between said second electrode and said casing is controlled;' an impedance ele-'" ment, and means governed in accordance with the relative ihdverarirtetweerr"said "first and end of said casing, first and second supports arranged in said casing, first and second electrodes respectively carried by said first and second supports and arranged in-spaced-apart facing relationship, said first support being rigidly connected to said diaphragm and movable therewith, said Second support being resiliently connected to said first support and movable freely with respect thereto, a movable mechanical system including a plurality of spaced-apart mass rings and a plurality of interposed stiiiness rings connected together to form a compact bellowlilze structure coupled to said second support and said casing, whereby the relative movement between said second electrode and said casing is controlled, an impedance element disposed between said electrodes, and means governed in accordance with the relative movement between said first and second electrodes for controlling the eifective impedance of said impedance element, whereby the variation in the effective imperance of said impedance element corresponds to sound energy to be transmitted.

3. A transmitter comprising first and second movable electrodes, means including a vibratory member for controlling the movement of said first electrode, a support, means including a movable mechanical system comprising a plurality of spaced-apart mass rings and a plurality of interposed stiflness rings connected together to form a compact bellows-like structure extending between and mechanically coupled to said second electrode and said support for controlling the movement of said second electrode, an impedance element, and means governed in accordance with the relative movement between said first and second electrodes for controlling the effective impedance of said impedance element.

chanically connected to said diaphragm, whereby the movement of said first electrode is controlled by said diaphragm, a second movable electrode associated with said first electrode, whereby the sound energy transmitted by said transmitter with said first electrode when said dia hragm is subjected to sound waves having low frequencies disposed in said audible range, whereby the background sound energy is filtered out.

HAROLD C. PYE.

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