US1719951A - Apparatus for finding the direction of sound - Google Patents

Description

July 9, 1929. w, WALKER 1.719.951

APPARATUS FOR FINDING THE DIRECTION OF SOUND Filed April 22, 1925 HIS A TTORNEYS.

WILLIAM L. WALKER, OF NEW YORK, N. Y., ASSIGNOR T WALKER SIGNAL & EQUIP- MENT GORPOBATION, A CORPORATIGN OF DELAWARE.

APPARATUS FOR FINDING THE DTRECTION OF SOUND.

Application filed April 22, 1925. $eria1. No. 25,011.

My invention relates to the detection of sound direction or e location of the source of sound by measuring the difference in sound intensity from a given source received at two diiierent locations, and has for its object the provision of: a simple, compact and eificient device of this character. While my invention is especially adapted for navigational purposes to detect the location of submarine signals and the like, it of course is not limited to such use.

My invention will be fully understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings, Figure 1 is a diagramof the1 circuits and apparatus of my invention, an

Fig. 2 is an ,end view of the microphone switch.

Referring to the drawings in which the nu.- merals 1 and 2 indicate two microphones, which may be of any preferred type, positioned in spaced relation. When my invention is used on board ship, one pair of these microphones is preferably positioned near the bow of theship and, another pair near the stern ofthe ship below the water line on the port and starboard sides respectively.

The fore and aft pairs of microphones are used in identical manners and therefore the use of one only will be described. The microphone 1 is connected on one side to a battery 3 and on the other side with contacts 4 and 5 positioned on opposite sides of a double throw switch 6. Microphone 2 is similarly connected with battery 3 and contacts 7 and 8 of switch 6. The switch blades 6', 6", are preferably of segmental form, as shown in Fig. 2. These blades are of sufiici'ent width to span respectively the contacts 4, 7 and 5, 8, when the switch 6 is in its neutral or middle position. The purpose of this arrangement is to short-circuit the microphones while the switch is operated to connect one or the other of the microphones and thereby prevent a clicking sound in the telephones. For example, when the switch 6 is in the full line position shownin Fig. 2, in which microphone 2 is connected with contactlO and it is desired to connect microphone 1 with contact 10, the switch 6 is thrown vto the right as indicated in dotted lines in Fig. 2. During this movement, microphones 1 and 2 are short-circuited 9 and 10 of switch 6 are connected to contacts 11 and 12 of switch13, and battery 3 is connccted with contacts 14 and 15 of switch 13 as shown. The blade 13 of switch 13 is similar to blades 6, 6" of switch 6, and shortcircuits the telephones while the switch 13 is operated to prevent clicking sounds.

It is thereforev clear that by throwing switch 6 to one side or the other, either of the microphones may be connected with switch 13. On switch 13, terminal 16'is intermediate contacts 11 and 12, and terminal 17 is intermediate contacts 14 and 15. The primary coil 18 of a transformer 19 is connected across' contacts '16, 17 by conductors 20, 21. A choke coil 22 is in parallel, and a condenser 23 is in series with the coil 18. A condenser 24 preferably is of the order of one microfarad and is connected with an intermediate point in the coil 18 and may be connected thereto by switch 25. The purpose of the condenser 24 and the switch 25 is to greatly increase the volume of sound transmitted by the microphones 1 and 2, when the signals are weak owing to greater distances. I have found that a condenser of about one microfarad capacitance has this effect over a wide range of frequencies, such as from to 1200 vibrations per second. Why this result is obtained, I cannot at present explain, but I have found that the volume is greatly increased irrespective of any question of resonance. From this itwill be seen that either of the microphones may be connected with primary coil 18 by switch 13. The switch 13 is also provided with contacts 26, 27, across which the secondary coil 28 is connected by conductors 29, 30, having a condenser 31 in parallel. The coils 18 and 28 are electrically similar and are wound on opposite poles 32 and 32 formed on a ring shaped yoke 33. Intermediate said poles is 42 which is graduated to indicate the direction of the source of sound from a comparison of the intensities of the sound at different points and the] adjustment necessary to balnected with either of the coils 28, 35. It will be apparent that the coil 28 is provided as "an additional secondary for the transformer in order to eliminate the necessity of turning the armature coil and its pointer 41 back to zero orto the positionof maximum effect when throwing the microphone producing the weaker signals into circuit. In other words, the coil 28 is used when listening to the sounds from the weaker microphone in place of the coil 35 in order to compare the current in the coil 28 with the current produced by the reduced volume of signals as determined by the position of the coil 35, without returning the latter to zero position. It will be obvious, however, that the transformer may be used with only the coils 18 and 35 if the, coil is turned to zero position each time the signals from the weaker microphone are listened to. The aft, starboard, and port microphones 1 and 2 may be connected with the switch 6 by means of the four pole switch 50, in which case the said aft microphones will be connected with the transformer and telephone circuits, and the procedure in finding direction astern is identical with that described in connectionwith the microphones 1 and 2.

Having described the structural details of my invention, its operation will be readily understood from the following brief description.

The switch 13 is thrown to the right to con= nect the telephone 45 with secondary coil 28, the coil 35 now being disconnected and inactive, so that lines of force may freely pass between the poles 32 and 32. The operator then operates switch ,6 to connect alternately.

microphones 1 and 2 with primary coil 18, and compares the intensities of the sounds of each. After having determined which of the microphone sounds the louder, the switch 6 is positioned to connect that microphone with switch 13, which, for purposes of illus t-rat-ion is assumed to be microphone 1. The switch 6 is thrown to the right The switch 13 is then thrown to the left to connect the telephone with coil 35, and this coil is manually rotated clockwise until the intensity frommicrophone 1 has been reduced to that of the weaker microphone, which in the case assumed is microphone 2, in which position the pointer 41 will indicate the direction of the source of sound as above set forth. If the operator desires to'make further comparisonsbctween the modified signal now heard from the microphone 1 andthe weaker imaeei forth prior to the detailed description will readily be reco nized. I do not wish to be understood as beinglimited to the details of form or arrangement of part herein set forth, for various changes may be made by those skilled in the art without departing from the spirit or scope of my invention.

What I claim is:

1. Appartus for finding the direction of sound comprising in combination two spaced microphones, a telephone circuit, a transformer having a fixed primary coil, a fixed secondary coil, said coils being on a common core, a movable coil positioned in the electromagnetic field of said transformer, said movable coil being mounted upon a core of such shape that the reluctance of the magnetic circuit through said fixed coils remains constant, means. for connecting the primary of said transformer with either of the microcommon core, said variable secondary being mounted upon a rotatable core of such shape that the reluctance of the magnetic circuit through said fixed coils remains constant, means for connecting the microphones alternat'ely with, said primary, means for connecting the telephone with said fixed secondary whereby the intensity of the sounds may be compared, means for connecting the telephone with said variable secondary whereby the inductive coupling between said primary coil and saidvariable secondary coil may be varied to reduce the intensity of thelouder sounding microphone to that of the other microphone, and means indicating the amount of variation of said variable sec ndary comprising a pointer movable there ith and a scale calibrated to indicte the direction of sound sources calculated from sound intensitie's.

3. Apparatus for finding the direction of sound comprising in combination two spaced microphones adapted to receive sound from the same source with unequal intensity, a telephone, a transformer having a fixed primary coil and a fixed secondary coil and a movable secondary coil, said fixed coils being ona common core, said movable secondary coil being mounted upon a core of such shape that the reluctance of the magnetic circuit through the fixed coils remains constant, means for connecting either of the microphones with said primary and means for connecting the telephone with said fixed secondary for the purpose of comparing the sound intensity of said microphones, means for connecting the telephone with sald movable secondary whlle the louder sounding microphone in connected core and a secondary coil on a rotatable mem-' ber positioned intermediate said fixed primary and secondary, said rotatable member being of such shape that the reluctance of the magnetic circuit through the fixed coils remains constant, means for connecting either of the microphones withsaid primary, means for connecting said telephone with either of the secondaries, and means indicating the amount of rotation of said member.

5. Apparatus for finding the direction of sound comprising in combination two spaced microphones adapted to receive sound from the same source with unequal intensity, a telephone, a transformer having a fixed primary coil and a fixed secondary coil on the same core and a secondary coil on a movable member intermediate said fixed primary and secondary coils, said movable member being of such shape that the reluctance of the magnetic circuit through 'the fixed coils remains constant, means for connecting either of the microphones with said primary, means for connecting the telephone with the fixed secondary whereby the intensity of the microphones may be compared, means for connecting the telephone with said movable secondary while the louder microphone is connected with the primary whereby the intensity thereof may be reduced to that of the other microphone by movement of the movable secondary, and means indicating the direction of the sound source comprising an indicator movable with said movable secondary and a cooperating scale calibrated to indicate directions for given intensities.

6. Apparatus for finding the direction of sound comprising, means for receiving sound waves and converting the same into correspondingly varying electric currents, a transformer having a metallic core, in circuit therewith and having stationary primary and secondary coils and a secondary coil relatively rotatable thereto in inductive relation with each other, said rotatable secondary coil being mounted upon a core of such shape that the reluctance of the magnetic circuit through the fixed coils remains constant, and means in circuit with the secondary coil of said transformer for detecting the vibrations of the received sound, and in which the reduction in intensity of the induced currents may be varied according to the angular position of said rotatable coil relative to that giving the maximum inductive effect.

7. Apparatus for finding the direction of sound comprising, means for receiving sound waves and converting the same into corre spondingly varying electric currents, a transformer in circuit therewith having a core of magnetic material, a primary coil, arelatively fixed secondary coil on the same core and a secondary coil rotatable in respect to said two coils and in inductive relation therewith, said rotatable secondary coil being mountedupon a core of such shape that the reluctance of the magnetic circuit through the fixed coils remains constant, means for detecting the vibrations of the received sound, and a switch for including either of said secondary coils in circuit with said detecting means.

8. A transformer for converting electric currents in accordance with sound vib 'ations received at two spaced microphones, having a core of magnetic material, a primary coil adapted to be connected with either of said microphones and a'plurality of secondary coils, one of which is mounted on said core, while the other is mounted on a rotatable core of such shape that the reluctance of the magnetic circuit through the primary coil and the first named secondary coil remains constant, whereby a comparison of the sound intensities at said microphones is obtained by the relative movement of said rotatable coil.

Dated this 16th day of April, 1925.

WILLIAM L. WALKER.

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