US1708938A - High-frequency sound signaling - Google Patents

Description

- p 1929- 1. B. CRANDALL ET AL. 1,708,938

HIGH FREQUENCY SOUND SIGNALING Filed Nov. 25. 1919 q I? Q 6 M15 p I a Mei/40H 5 557293 fiztenterl Apr. 16, 1929.

UNITED rArs IRVING B. GRANDALL, .OF EAST ORANGE,

NEW JERSEY, AND MARION s. ESTES, or

NEW YORK,- N. Y., ASSIGNORS 'L O WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

HIGH-FREQUENCY SOUND SIGNALING.

Application flied-November 25, 1919. Serial No. 340,471.

This invention relates to high frequency sound signaling and more particularly to devices used in submarine signaling for receiving high frequency sound and pro '5 ducing indications therefrom. .7

An object of the invention is to provide selective means for receiving high frequency sound-energy.

. Another object of the invention is to provide a microphone receiver for receiving and responding to sounds of ultra-audible frequency.

I An additional object of the invention is to provide a microphone mechanically tuned 16- to sound energy. 0 a given high frequency. A further object 'of the invention is to provide a microphone capable of responding to high frequency sound waves in water.

A still further object of the invention is to provide a receiving system for high frequency submarine sound transmission.

According to this invention a solid back microphone is constructed with. a carbon movable front electrode which may be spherical. The movable electrode is rigidly fixed to a thick metal diaphragm of such dimensions as to have a natural period corresponding to that of the high. frequency sound waves to be received. a The tuned 3o microphone so designed acts to produce high frequency variations in an electric current passing therethrough and these high frequency electric current variations "are detected in well known manner.

Referring to the drawing, Fig. 1 illustrates diagrammatically a high frequency submarine sound-receiving arrangement; Fig. 2 illustrates in section a tuned microphone receiver; Fig. 3 a section of a microphone; and Figs. 4; and 5 illustrate modified forms of the tuned diaphragm employed in the construction of Fig. 2. p

In the receivin system of Fig. 1 a high frequency microp one receiver 1 is s own in circuit with a source 2 of unidirectional current and the primary winding of a transformer 3, the secondary winding of which is in the input circuit of a detector 4 .of

high frequenc electrical currents. detector is pre erably of the thermionic discharge type. Associated with the input cir- This cuit of the-detector by means of a transformer 5 is a local source 6 of high frequency electric currents which may be of the same frequency as that of the sound waves to be received, as in the case of telephony; or may be of a different frequency as in telegraphic or teledynamic control transmission. 4 is connected in well-known manner to an amplifier 7 by which low frequency currents resulting from the detecting action are amplifiednnd supplied to a receiver 8 connected thereto.

In operation, the high frequency sound waves in water or other medium in which source 6. If heterodyne operation is to be employed the frequency of source'6 will be made'difl'erent from that of the incoming sounds. For telephony, as explained in United States Patent No. 1,330,471, patented- February 10, 1920 to B. W. Kendall for high frequency signaling, the current produced by the local generator will preferably be of the same frequency as the incoming sound waves. The detector 4 acts to combine the two electrical waves to produce in the output circuit a low frequency current component corresponding, in the case of heterodyne operation, to the beat difference note of the two electromotive forces supplied, and in the case where the local source 6 produces currents of the incoming wave frequency, telephonic or otherlow fre- The output circuit of detector be any signal receiving or indicating device or in the case of teledynamlc control transmission, a selecting or controlling element.

As shown-in Fig. illustrating the tuned microphoneu'eceiver, a microphone casing 9 of conducting materiahhas secured there in by means of insulating material 10-, such as wax or rubber, a stem portion of a solid ba K member .11 of a ll1lCI'Opl10IlG..

The front electrode or button 12 of the n1icro,-

' phone is attached by means of a-screw 18 to tuned diaphragm 14 which is preferably of disc shape and is clamped against an annular seat by means of-clamping ring 16 and bolts 17, attaching said ring to the seat portion of the casing. Conducting ,leads 18 are introduced into the casing 9 through an insulating sleeve 19. passing axially through a threaded bushing 20 of insulatingmaterial fitted in a' threaded recess in the casing. One of the leads is'el'ectrically connected to the casing and. the other to the stem of the back member of the microphone, so that cur I compact shape insuring rigidity and fits into a central openingof washer 23, to which it is attached by glue or other adhesive material 25. Cup 21 is fitted interiorly with a cylindrical insulating member 26 and inside of this vcup and-adjacent its back wall a thin carbon disc 27 and a metallic disc 28 globular or of the'ordinary form are placed within the cup 21 and are retained by washer 23. The front electrode 12 bears against the granules and because of its shape produces large variations in pressure for slight displacements of the diaphragm.

- The diaphragm 14L maybe a plane disc, as shown in Fig.2, or may be recessed, as

indicated in Figs. 4 and-5. For high frequency operation the microphone receiver may be made selective of a particular frequency by so designing the diaphragm that it is mechanically tuned to the desired fre quency. In accordance with the well known laws of tuning 'of clamped plates the frequency of the diaphragm may be made high by increasing its stiffness and decreasing its mass. Consequently, material of low atomic mass such as aluminum, may be used, and

.the diaphragm may be made relatively thick in' proportion to its diameter.

any

In the modifications of Figs. 4 and 5 the ,diaphragmis .shown centrally recessed so that the thickness at the. center is considertothe tuned diaphragm and is made rigid and compact so that the electrode will be forced to partake of the high frequency movement of the diaphragm, and the variations in the microphonic current will correspond in frequency and in amplitude to the sound wave energy received.

In practice, operating at .a frequency of 80,000 cycles per second, the diaphragm has. been made ;of aluminum, the clamping ring having an internal diameter of an inch. With the form 'of diaphragm shown in Fig. 4, the minimum thickness of the diaphragm was made one-eighth of an. inch, and the' thickness at the periphery one-quarter of an inch. The front. electrode was a spherical carbon diameter.

' It is to be understood that the specific circuit and structural details, as well asthe f The front electrode 12 is rigidly attached I ball; five-sixteenths v of an inch in I dimensions .recitedherein, are given merel 1 byway of example of aconstruction whic has been found satisfactory in practice, and that the invention is not to be' limited thereto, but only by the scope of the appended claims.

.VVhat is claimedisz 1.' An acoustical 'dia hragm comprising a disc the thickness ofgwh ch varies symmetrically with respect to itscenter, said disc being composed of material of such atomic mass relatively to its diameter and thickness that, .when clamped at its periphery, it substantially excluslvely vibrates ata single superaudible frequency. are placed. Carbon granules 24 of semi- 2. A tuned high frequencyacoustical diaphragm comprising an'alummum disc substantially thinner at its center than at any other point and which has a generally lenslike form.

3. A tuned high frequency acoustical dia phragmcomprising a disc, the thickness of 415 which decreases progressively from its periphery towards its center.

4. An acoustical diaphragm comprising a disc whose thickness varies symmetrically with respect to its center and is minimum at the center, the atomic mass relatively to the rial, a substantially spherical conducting button, a thin flexible retaining member attached to said button and serving to close -said cup, means insulating said button from said cup except through said granular material, a tuned diaphragm rigidl connected to said button, and terminal e ements attached to said button and said cup whereby a circuit may be completed therebetween and through said granular material.

7. A solid back microphone sound receiver comprising a casing, a cup containing granular material rigidly attached thereto, a conducting button having a substantially spherical surface in engagement with said materia1, means insulating said button from said cup except through said granular material, a tuned diaphragm rigidly connected to said button, and terminal elements attached to said button and said cup whereby a circuit may be completed therebetween through said granular material.

8. A solid back microphone sound receiver comprising a rigid casing member having a front opening, a diaphragm closing said opening, a microphone carried thereby and secured at the back-of. said casing member,

and means whereb said diaphragm may ac tuate said microp one, said diaphragm being of such atomic mass and relative dimensionsto be tuned to a definite superaudible' frequency.

In witness whereof, we hereunto subscribe our names this 19th day of November, -A. D.

4 IRVING ORANDALL.

MARION s. ESTES.

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