US2508544A

US2508544A - Electroacoustic transducer device

Info

Publication number: US2508544A
Application number: US731786A
Authority: US
Inventors: Harry B Shaper
Original assignee: Brush Development Co
Current assignee: Brush Development Co
Priority date: 1947-03-01
Filing date: 1947-03-01
Publication date: 1950-05-23
Anticipated expiration: 1967-05-23

Description

May 23, 1950 H. B. SHAPER ELECTROACOUSTIC TRANSDUCER DEVICE 2 Sheets-Sheet 1 Filed March 1, 1947 R R E mp EH W5 B VI R R A H May 23, 1950 H. B. SHAPER 2,508,544

ELECTROACOUSTIC TRANSDUCER DEVICE Filed March 1, 1947 2 Sheets-Sheet 2 Cousrnu'r Von/me HMPLIFIER INVENTOR. HARRY B. SHAPER ATTORNEY Patented May 23, 1950 .7 .s a

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2,508,544 ELEWRQAQQUSTIQ TRANSDUCER DEVICE- Harrr B- Shaper, Asto ass g or'to Th Brush ev. opmentflp npany, Q1eveland ,'0lrio,

ss rersfi i -071 i! Application March -1, 1947, Serial'No. 731,788

' a c aims t iiri Myinvention pertains to a transducerhaying brought out through holes-22 in the base 20 and a variable frequency response pattern. are connected to a number of solder lugs 23rse-' Anobject of my invention is to providea transcuredto theback faceof the base Zllby meansof ducer'whose frequency response pattern can easily screws 24.

be changed. 6- A cup-shaped housing 2], referably formedoi A further-object of my invention is to provide a an insulating material such as Bakelite, and hardtransducer having a directional pattern in the ing a cable inlet opening to accommodate the form of a beam, the breadth or spread of which cable 2181s provided. A grommet-29 isinsertedin may easily be controlled. the cable'opening and a cableclarnp 3 is secured Other objects and a fuller understanding of my to the inside of the housing 2-! to prevent the cable invention may be had-by referring to the followfrom pulling out of-the housing. The cable is ing description, claims, and drawings, wherein: comprised of a number of wires, including, a, Figure 1 is a sectional side view of a transducer ground wire which; may be the cable shield, and

embodying'my invention. these wires are soldered to their respective solder Figure 2 is a plan view, on an enlarged scale, lug 23. Thehousing 21 is then slippedover the of a portion of the transducer shown in Figure 1. base and a plurality of screws are put in Figure 3 is a schematic view, on an enlarged placetosecure them together.

scale, illustrating the electricalconnections in the Figure 2 is a plan View, von an enlarged scale,

transducer shown in Figures 1 and 2, and of the transducer assembly l5 with the diaphragm Figures 4 and 5 are frequency response dia- 20 I! partially broken away. The expander piezograms showing some of the patterns obtainable electric crystals are arranged in a plurality of with the transducer shown in Figure 1. rings" B and C about a central group A, and the With reference to the drawings, my transducer individual crystals which comprise each group comprises a parabolic reflector l0 formed of metal preferably re c nne d in p a a is s own or other material having satisfactory vibrational 25 in Figure 3. A constant voltage amplifier is wave-reflecting properties. The narrow portion connected through a selector switch 3| in such of the reflector I0 is turned inwardly toward its at ma that a y o of t y a groups focal point l3 until it lies in a plane substantially B or C can be energized by itself, or in combinaperpendicular to the axis of the reflector, and a i wi either of the other tw o p o n large circular opening I4 is provided in this planar 3 com ination with bo h of he oth r w ro psportion. n With only the crystal group A energized the V A transducer assembly, indicated generally by directional pattern of the transducer and rethe reference character I5, is connected to the refl r Will be s i c d by the pattern A in flector In by means of a plurality of screws l6 ure With o y t e ring B energized it 1 with the transducer diaphragm l1 substantially 85 be as indicated by the pattern B, and with only closing the opening [4 in the narrow nd of th the ring C energized it will be as indicated by the reflector l0, and with the center of the diaphragm pattern C. The sharpest (or most directional) located at the focal point I3 of the parabolic repattern is obtained with the use of the group A flector. because they are located substantially at the The transducer assembly I5 is comprised of a focal point l3 of the parabolic reflector, and vimassive base 20, preferably made of Bakelite or brational waves emanating from the focal point some other hard, stable, insulating material, havand Sp eadin in all directions therefrom will ing a cavity I8. A diaphragm I1 is secured to strike the parabolic reflector l0 and be reflected the base 20 by means of screws 19 and is so posiina beam substantially parallel to the axis of the timed that it closes the cavity l8 in the base 20. reflector. Because the crystal rin B and C are A plurality of expander transducer means 2| located away from the focal point l3 their patare positioned within the cavity with their end terns will be broader than the pattern of the A faces secured in engagement with the base 20 gro p, as is shown y igure 4. Accordingly, by and with the diaphragm IT. The transducers connecting the crystal groups A, B, and C 'so that preferably are expander piezoelectric crystal eleany combination of one or more of them can be ments so oriented that a direction of expansion energized by the amplifier 30, directional patterns and contraction is perpendicular to the plane of are easily obtainable which vary from the inthe diaphragm l1, although other transducer dividual patterns shown in Figure 4 to the pattern means such, for example, as the magnetostrictive shown in Figure 5 when all of the crystal groups type may be utilized. The transducer leads are are simultaneously energized.

While I have described the operation of my invention with the amplifier 30 energizing the crystals, i. e., as a loudspeaker, it is to be understood that it operates just as well as a microphone device wherein the several crystal groups, either singly or together, generate voltages in accordance with a received pressure wave and control the amplifier 30 in accordance therewith.

While not essential, it may be desirable that the energy given out by the several groups of crystals (when operating as a speaker) should be equal. This may be achieved by making equal the total area of the end faces of the crystals in the several groups A, B and C, as is shown in Figures 2 and 3.

My invention is adapted for use in air or liquid, although the construction shown in Figure 1 is particularly useful in air. Suitable modifications may easily be incorporated to make the device useful under water.

Whether a device constructed in accordance with my invention is used in air or liquid, it has its sharpest directional characteristics at the higher frequencies, and in any event the length of the path from the focal point 13 to the parabolic reflector and the width of the mouth of the reflector should be about five times the length of the longest wave in the medium in which the device is operating.

While I have described my invention with a certain degree of particularity, it is to be understood that it has been by way of example and that changes can be made without departing from the spirit and scope of my invention.

I claim as my invention:

1. In a transducer, an open parabolic reflector of sound-waves having an axis of symmetry,

first expander electromechanical transducer means located substantially at the focal point of said parabolic reflector, second electromechanical transducer means comprising a plurality of individual transducers all connected in parallel located symmetrically around said first transducer means but away from the said focal point, said first and second transducer means facing the open end of said reflector and adapted to expand in a direction parallel to said axis, amplifier means, first and second electrical circuit means connected, respectively, to said first and second transducer means; and switch means for connecting said first and said second transducer means individually to said amplifier, and for connecting said first and said second transducer means simultaneously to said amplifier.

2. The invention set forth in claim 1, further characterized in this: that the area of the end face of said first transducer means is substan-- tially equal to'the area of the end face of said second transducer means.

3. A transducer as set forth in claim 1, further characterized by said amplifier means being a constant voltage amplifier.

HARRY B. SHAPER.

REFERENCES CITED The following references are of record in the