US2628289A - Suspension system for dynamic microphones - Google Patents

Description

Feb. l0, 1953 Y H. F. OLSON ETAL v 2,628,289

' l SUSPENSION SYSTEM .Foa DYNAMIC MICROPHONES Filed 0013. 29, 1949 nnentors v sm HARRY; F. l'JLsnN 3Q- Patented Feb. 10, 1,953

UNITED STATES PATE-NT OFFICE Application October 29, 1949, Serial No. 124,462

7 Claims.

This invention relates to a suspension system for sound translating apparatus, and more particularly to a shock mounting for a dynamic microphone which will isolate the motor assembly thereof from mechanical vibrations originating in the support therefor.

In the art of sound translation, the microphone, which is employed for converting sound wave energy into electrical energy, is usually mounted on some kind of support. Where the microphone is used in connection with motion picture or television sets, or the like, it is found desirable to employ a movable type of support, such as a boom, because of its freedom of movement in all directions and the fact that the microphone can be suspended above and in close proximity to the source of sound. The microphone is, of course, not only sensitive to sound wave energy, but also to external mechanical vibrations which may be transmitted thereto through the body of the instrument. Therefore, when the microphone is used on a boom, for example, the problem of reducing not only shock excitation of lthe microphone due to swift and sudden movements of the boom, but also mechanical resonances transmitted to the microphone -because of movement of the boom, is of major importance. As constructed heretofore, microphone supports employV a compliant mounting between the boom and the microphone to overcome these disturbances. While this type of mounting is, no doubt, satisfactory for many applications, in the case of a very sensitive microphone, there is insuic'ient mechanical filtering provided.

The principal object of our present invention, therefore, is to provide an improved suspension system for a microphone.

Another object of our present invention is to provide a flexible support for a microphone which is more efficient in preventing mechanical vibrations originating from movement of the microphone and its support from interfering with the proper operation of the microphone.

It is also an object of our present invention to provide a more eiiicient mechanical filter and support for the motor assembly of a dynamic type microphone.

Still another object of our present invention is to provide a double shock mounting for a dynamic type microphone which will eliminate undesirable response resulting from movement of the microphone and the support therefor.

A still further object of our present invention is to provide a simple and highly efficient shock proof andvibration proof mounting forcthe motor assembly of a dynamic type microphone.

In accordance with our present invention, we provide a double shock mounting for a dynamic type microphone the response characteristic of Which is controlled through use of an acoustical resistance element mounted behind at least a portion of the vibratile'cor-rductor' element. Two exible supports' or connectionsy are provided for isolating themotor elements of the microphone from the supporting structure which may be a boom, stand, or the like. A first flexible connector, or outside shock mount of conventional type, is disposed between the supporting structure andy the main body of ther microphone which may comprise the acoustical resistance means. A second flexible connector or internal shock mount is disposed between the main body of the microphone or acoustical resistance means and the magnetic field structure of the microphone motor assembly, with a flexible connection provided between the acoustical resistance means andthe member thereof which closes off the portion of one side of the vibratile conductor element.

The novel features4 characteristic oiour invention, as well as additional objects and advantages thereof, will be better understood from the following detailed description when read in connection with the accompanying drawing in which Figure 1 is a perspective" view of a dynamic microphone and a suspension system therefor in accordance with our present invention', the microphone being shown attached to the end of a support and with the protective screen therefor removed,

Figure 2 is an elevation, partly in section, of the microphone in Figure l, illustrating certain details of construction relating to the flexible connectors, and

Figure 3 is a sectional View taken on the linev 3 3 of Figure 2.

Referring more particularly to the drawing, wherein similar reference characters designate corresponding parts throughout, there is illustrated in Figure 1, a conventional, dynamic microphone I supported from the end of a support 3, such as a microphone boom, stand, or the like.

The microphone I is of the unidirectional type more particularly disclosed in Olson Reissue Patent No. 19,115, granted March 13, 1934, and comprises a conventional motor assembly 5 for translating sound "wave energy into electrical energy, and acoustical resistance means l which is mounted in a support or casing 8 and is operatively vassociated with the vibratile conductorvelement 9 of the motor assembly 5 for controlling the directional response characteristic of the microphone. The motor assembly comprises a vibratile element or thin, elongated, conductive ribbon 9 of well known form, and a suitable magnetic 'eld structure I I. The magnetic field structure I I comprises a pair of magnets I3 each having a pole piece I5 mounted on an end thereof and being connected at their opposite ends by a magnetically permeable base plate I6. The pole pieces I5 are disposed in spaced apart relation to each other, and the vibratile element 9 is suspended for movement in the air gap or space between the pole pieces in response to sound wave energy impinging thereon, in a manner well known in the art.

The acoustical resistance means 1 comprises an elongated, closed pipe I1 which may be constructed in the form of a labyrinth structure composed of a plurality of interconnecting tubes or pipes I8 lled with tufts of felt or similar damping material I9 and more particularly disclosed in Olson Patent No. 2,271,988, granted February 3, 1942. The open end 2| of the labyrinth structure I1 is connected by a flexible coupling member 23 to a suitable pipe or labyrinth connector 24 (shown partly in section in Figure 2) mounted behind at least a portion of the vibratile ribbon conductor element 9 to close off one side of that ribbon portion from sound waves, in a manner more particularly disclosed in the above-identified Olson reissue patent.

In accordance with our present invention, there is provided a double shock mount for the microphone I which comprises separate compliant mounting members 21, 29. The principal or outer shock mounting member 21 may be of any conventional or suitable type, and comprises an annular, flexible element 3|, such as soft rubber, or the like, the peripheral edges of which are clamped, or otherwise secured, between a pair of annular ring members 33, 35. The ring members 33, 35 are provided with apertured tabs 31 for attaching the outer mounting member 21 to a suitable support in any convenient manner, such, for example, as the adjustable connection provided by the wing nut 39 and bolt 4I attached on the end of the support 3, as shown in Figure l of the drawing. The flexible element 3| is also provided with a plurality of apertures 43, the purpose of which is to increase the flexibility of the element 3 I.

A central aperture 44 is provided in the flexible element 3| for receiving the microphone I. For this purpose, the top plate 45 of the microphone casing 8 enclosing the acoustical resistance means 1 is provided with an outwardly extending flange 41. An annular ring 49 cooperates with the flange 41 to clamp the inner periphery of the flexible element 3| dening the central aperture 44 therebetween thereby to flexibly support the microphone I.

'Ihe motor assembly 5 is supported by the secondary or inner shock mounting member 29, which is also constituted of flexible material, such as rubber, or the like, and which also serves to connect it to the support or casing B. The inner shock mounting member 29 is somewhat rectangular in cross section and has one end thereof securely attached by cementing or other suitable means to another annular flange 5I provided on the top plate 45 of the microphone casing. The Y opposite end of the inner shock mounting member 29 is also attached by cementing or other suitable means, to an annular flange 53 provided on the base plate I6 connecting the magnets I3.

Thus, a secondary mounting means supports the motor assembly 5 and comprises a rst flexible tubular member 29 connecting the motor assembly and the support or casing 8, and a second flexible tubular member 23 connecting the acoustic resistance means 1 and the pipe or labyringth connector 25.

It will be recognized by those skilled in the art, that we have provided an improved shock mounting for isolating the motor assembly of a dynamic type microphone from shocks or mechanical vibrations originating in the microphone support. While we have described and illustrated but a single embodiment of our present invention, it will also be recognized that various changes and modifications are possible Within the spirit of our invention. Therefore, we desire that the particular form of our invention described herein shall be considered as illustrative and not as limiting.

What is claimed is:

1. In a dynamic microphone, the combination of a motor assembly comprising means for producing a magnetic field and vibratile conductor means mounted in said magnetic field for vibration in response to sound Wave energy, means associated with at least a portion of said vibratile conductor means constituting a terminating acoustic resista-nce therefor and including a supporting device, and flexible means connecting said motor assembly to said supporting device thereby to flexibly support said motor assembly from said supporting device.

2. A dynamic microphone according to claim 1 wherein said terminating acoustic resistance means comprises a tubular connector element mounted behind said portion of said vibratile conductor means, said vibratile conductor portion substantially closing one end of said tubular connector element, an elongated pipe, and a flexible coupling connecting one end of said pipe with the opposite end of said tubular connector.

3. In combination with a dynamic microphone comprising a motor assembly including vibratile conductor means, and means associated with said motor assembly constituting a terminating acoustic resistance for said vibratile conductor means, said acoustic resistance means including a support member therefor, a flexible mounting therefor comprising a first flexible mounting means attached to said acoustic resistance means support member and adapted for attachment to a support for said microphone, and a second flexible mounting means connecting said motor assembly to said acoustic resistance means support member for flexibly supporting said motor assembly therefrom.

4. The invention set forth in claim 3 wherein said first flexible mounting means comprises an annular member having a central aperture therein, and wherein said microphone extends through said central aperture, said acoustical resistance means support member being attached to said rst flexible member at the inner peripheral edge thereof defining said central aperture.

5. The invention set forth in claim 4 wherein said rst flexible mounting means is provided with means adjacent the outer peripheral edge thereof for attaching said first flexible mounting means to a support for said microphone.

6. The invention set forth in claim 3 wherein said second flexible mounting means comprises a rst, flexible tubular member having opposite ends thereof secured respectively to said motor assembly and said acoustic resistance means support member, wherein said microphone also includes a pipe behind at least a portion of said vibratile conductor means, and wherein there is included a second, exible tubular member connecting said acoustic resistance means and said pipe.

7. A mechanical lter for supporting on a movable support the motor assembly of a dynamic microphone having an acoustical resistance means associated with the vibratile conductor element thereof, said acoustical resistance means including an enclosing casing therefor, said mechanical filter comprising, in combination, a first iiexible member connecting said acoustical resistance means casing to said movable support, and a second exible member connecting said motor assembly to said acoustical resistance means casing for flexibly supporting said motor assembly therefrom.

HARRY F. OLSON. JOHN PRESTON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,178,216 Anderson Oct. 31, 1939 2,271,938 Olson Feb. 2, 1942 FOREIGN PATENTS Number Country Date 506,668 Great Britain June 1, 1939

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