US2065456A - Sound damping device for microphones - Google Patents

Description

Dec. 22, 1936,. J. A. HAYE-NGA ET Al. 2,065,456

soUND DAMPING DEVICE ma MIcRoPHoNEs Filed Feb. 13, 1936 rE-5. 5- wvo/us Jac/r .Hage/1712 Euh/r E. raa/f Patented Dec. 22, 1936 UNITED STATES PATENT OFFICE SOUND DAMPING DEVICE FOR MICROPHONES Jack A. Hayenga and Frank E. Brooks, Yakima,

Wash., assignors of one-half to Richard 0.

7 Claims.

This invention relates to a sound damping device for microphones or other devices for the transformation of air vibrations or sound waves into any one of several forms of energy.

When used with a radio microphone, for example, the improvements increase the energy level of all frequencies picked up, at the lower and higher extremes of the audio range, increases the purity and accuracy of transformation of all frequencies and generally reduces the diiii- `culties encountered vwith the acoustics of a broadcasting studio.

One feature of the invention resides in arranging on one side of a vibrating member used to transform sound waves into any one of several forms of energy, a series of convolutions of sound absorbingmaterial arranged in such a manner as to reduce the frontal area and the angle of incidence presented to the sound waves approaching the sound absorbing material from the vibrating member, to a minimum; and with alternate convolutions closed with sound absorbing material on the sides away from the Vibrating member in such a manner as to form relatively dead air spaces and with the sound absorbing material arranged within a suitable baffle which is attached to the structural member, or members, associated with the vibrating member by means of suitable vibration damping material.

The use of the present sound damping device in connection with a radio microphone enables the use of an effective bafe so that the energy level is raised for all frequencies and the discordant reflected waves are eliminated.

The more specic objects and advantages will become apparent from a consideration of the description following taken in connection with the accompanying drawing, illustrating an operative embodiment.

In said drawing:-

Figure 1 is an end elevation of one form of the invention;

Figure 2 is a side elevation thereof;

Figure 3 is a central vertical longitudinal sectional view;

Figure 4 is a central horizontal sectional view taken on the line 4 4 of Figure l;

Figure 5 is an enlarged detail of the frames and sound absorbing material thereof;

Figure 6 is a detail perspective view of one of the frames on which the sound absorbing material is mounted; and

Figure '7 is a fragmentary detail of a modied means for supporting the casing of the invention.

Referring specically to the drawing, wherein like reference characters designate like or similar parts, 8 designates a casing or enclosure which is made of solid wood, composition material or the like of such thickness, say an inch or more, as to be practically non-resonant at the frequen- 5 cies in the associated microphone range. 9 designates a hollow tubular pedestal for supporting the casing 8. The microphone I0, of conventional form, is mounted in an opening II in one end of said casing, surrounded by vibration damping material I2, such as rubber, felt or the like. The interior of the casing 8, has a lining I3, of sound damping material, such as cloth, batting or the like.

Within the casing, any suitable number of sound damping units I4 are provided. These units are similar in construction and consist of skeleton metallic Wire or other frames I5 having parallel rods or wires I6 at the rear thereof and parallel rods or wires I'I at the front thereof, the latter being disposed in planes passing between the planes of the rst mentioned wires I6. Sheets I8 of sound deadening material or sound absorbing material are laced alternately over the wires I6 and I'I in accordion fashion, having their ends secured to the adjacent parts of the frame and such ends or the frame secured to the material I3 and the casing I0. To this end, the material I3 and I8 may be glued to each other and to the casing I 0, or nails, tacks or other suitable means may be driven through the material I3 into the casing and about the frames.

It will be noted that alternate convolutions or valleys of the material I 8, at the sides of the frame remo'te to the microphone are closed by means of strips I 9 of sound absorbing material, stitched or otherwise fastened at its sides to the material I8.

Three of the sound damping units I4 are shown in the drawing and the central one is turned at to the remaining ones.

The sound absorbing material I3, I8, and I9, for example, may be cotton, bathrobe material constructed with forty-nine warp threads per inch and forty-eight lling threads per inch, manufactured thirty-six inches wide and weighing eight ounces per yard. It is to be understood that any suitable sound absorbing material may be used.

The effect of closing alternate convolutions on the sides of the units I4 away from the microphone is to delay and divert the sound waves traveling that path so that these waves are more effectively damped. In practice, this arrangement is highly successful whereas when all con- 55 volutions are closed, the sound Waves are reflected back to the microphone too much and when no convolutions are closed, the damping is insufficient. The purpose of the 90 shift of the central unit I4 is to change the direction of the sound Waves so that they are more effectively broken up or damped than would be the case if the convolutions all had the same position.

20 designates an electric conductor from microphone IU, that exits from casing 8 through an insulation walled opening 2| into the support 9 and from thence through an opening 22 in said support.

In Figure '7 is disclosed a modified means for supporting the casing 8 `comprising an angular bracket 23 for suspending the casing, the electric conductor being designated 20 that exits through insulated opening 2| and secured to a leg of the bracket 23 by loops 24.

It is to be understood that the exact form of the convolutions or pleats may be varied from the simple accordion form shown to more complex forms of circles, zigzags, spirals, etc.

Various changes may be resorted to provided they fall Within the spirit and scope of the invention.

We 'claim as our invention:-

1. A device of the class described comprising a casing in one end of which a microphone is adapted to be positioned, and sound absorbing materia-l in said casing arranged in convolutions and a skeleton support for said material having means to facilitate the lacing and support of the convolutions.

2. A device of the class described comprising a casing in one end of which a microphone is adapted to be positioned, said casing being substantially non-resonant to the vibrations of a microphone.

and sound absorbing material in said casing arranged in convolutions and a skeleton support for said material having means to facilitate the lacing and support of the convolutions.

3. A device according to claim 2 having the alternate convolutions at the side remote to that in which the microphone is adapted to be positioned closed by sound absorbing material.

4. A device according to claim 2 having the convolutions extending generally in the direction of the longitudinal axis of the microphone positioning end and the convolutions at the end remote thereto being alternately closed with sound absorbing material.

5. A device of the class described comprising a casing in one end of which a microphone is adapted to be positioned, a skeleton frame within said casing disposed transversely thereof, sound absorbing material laced in convolutions in said frame, alternate convolutions at the side of the frame remote to the microphone receiving end being closed by sound absorbing material.

6. A device according to claim 5, having sound absorbing material lining said casing.

7. A device of the class described comprising a casing in one end of which a microphone is adapted to be positioned, skeleton frames Within said casing disposed transversely thereof, sound absorbing material laced in said frames and forming convolutions, the convolutions of one frame being angularly disposed with respect to the convolutions of the other frame, alternate convolutions at the sides remote to the microphone receiving end being closed by sound absorbing material.

JACK A. HAYENGA. FRANK E. BROOKS.

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