US3548121A

US3548121A - Foam material support means for a sound transmitter

Info

Publication number: US3548121A
Application number: US645238A
Authority: US
Inventors: Rudolf Goerike; Konrad Wolf
Original assignee: AKG Akustische und Kino Geraete GmbH
Current assignee: AKG Acoustics GmbH
Priority date: 1966-06-17
Filing date: 1967-06-12
Publication date: 1970-12-15
Anticipated expiration: 1987-12-15
Also published as: NL6708350A; GB1159443A; AT265384B; DE1512667A1

Description

United States Patent inventors Rudolf Gorike Vienna; Konrad Wolf, Bad Vosiau, Austria Appl. No. 645,238 Filed June 12, 1967 Patented Dec. 15, 1970 Assignee Akustische u. Kino-Gerate Gesellschait m.b.H. Vienna, Austria Priority June 17, 1966 Austria No. A5820/66 FOAM MATERIAL SUPPORT MEANS FOR A SOUND TRANSMITTER 6 Claims, 10 Drawing Figs.

US. (I 179/184, 179/ 146 hit. (I H04r 1/02 Field olSearch 179/184,

187, 188, 12iDlR, 121, 107, 146, ll5.SBS(Cursory) [5 6] References Cited UNITED STATES PATENTS 3,236,328 2/1966 Burroughs 179/184 2,718,563 9/1955 Nicholides..... 179/107 2,477,698 8/1949 Little 179/ 107 Primary Examiner-Kathleen l-l. Claffy Assistant Examiner-Thomas W. Brown Attorney-Me Glew and Toren ABSTRACT: Within a sound transmitter housing, open cell foam material is arranged within a rigid casing to support the various transmitter elements spaced inwardly from the casing and to protect them against wind and shock. Openings are provided in the housing casing to permit sound to reach the sound inlet openings in the transmitters transducing means. The foam material completely fills the spaces between the housing casing and the sound inlet openings of the transducing means and is in contacting relationship with the 'transducing means and the housing. The transducing means is provided by moving coil microphones of unidirectional pattern disposed either side-by-side or in axial alignment within the housing. Alternatively, the foam material may be composed of one or a number of layers: where multiple layers are employed, their characteristics vary with their function within the housing.

PATENIED DEC] 5 I976 FIG. lb

FIGS

INVENTORS RUDOL F GORIKE BY KoIvRno um;

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1 FOAM MATERIAL SUPPORT MEANS FOR A SOUND TRANSMITTER SUMMARY or THE INVENTION The present invention is directed to a support for the transducing elements within a sound transmitter housing and more particularly, to an open cell foam material for both supporting and protecting the transducer elements from wind and shock.

it is generally well known that microphones, particularly those utilized for transmitting a wide frequency band, are extremely sensitive to both shock and wind. To eliminate the ef fect of wind on such microphones, it has been usual to provide a resilient mounting for the microphones'within a wind screen. in such an arrangement, a mechanical deviceis needed as a support for the resilient mounting for the microphone and also to attach the wind screen to the microphone housing. This arrangement has proved to be relatively. expensive and the microphone, with such an assembly mounted on it, is rather unwieldy. More recently, a newmaterial made of an open cell foam of polyesters, and specifically of polyurethanes, has been used as the windscreen material. This open ce'll foam is commercially available and is notable by a complete absence of membranes within its interior. Open cell foam materials of polyurethane provide a skeleton structure having a multiplicity of columns which define a large number of hexagonal cavities, amounting to about 97 percent of the total volume of the foam. During the manufacture of the foam material the size of the cavities or pores within the foam can be varied within wide limits so that an optimum pore size can be. obtained for any purpose.

in utilizing the open cell foam as a windscreen, as mentioned above, a cap of the foam is. formed into the proper shape and fitted over the sound inlet openings of the microphone. While this arrangement has, resulted in an adequate protection for the microphone frorn wind, a special mechanical structure was still needed to protect it from shock.

Accordingly, the present invention is directed to the use of an open cell foam in a sound transmitter to protect the trans ducing means from both wind and shock.

Specifically, the invention relates to a two-channel sound transmitter arranged within a single housing and comprising individual moving-coil microphones having a unidirectional pattern, and more preferably a cardioid pattern. In such a sound transmitter, the transducing or microphones as well as the structural and circuit elements are embedded in an open cell foam material which completely fills the interior of the housing. Additionally, the housing provided with openings or is formed of a suitable material permitting sound to reach the microphones within its interior.- 1 t For use within the sound transmitter housing, the open cell foam material is formed into a body havinglopenings which conform to the shape of the microphone and the other structural or circuit elements located within the housing. Alternatively, the body of foam material may be'formed as a unitary member or it may be divided into two or more parts. Where a unitary member is used, openings extend into the foam material for holding the microphone and the other transmitter elements. The unfilled portions of the openings which remain after the transducers and other elements are inserted, are filled with discs or plugs of the foam material so that all of the parts in the housing are completely enclosed.- Where two parts form the body of foam material, the parts establish a joint or parting plane which intersects or is arranged tangential to the openings for the microphones and the other elements. Additionally, other openings, may be provided as necessary.

In some instances, it has been found preferable to form the body of foam material out of a plurality of layers, for example, the structural elements of the sound transmitter may be em bedded within a relatively thin layer of foam material characterized by a high elasticity and a difi'erent pore size from the remaining layers. The difference in the various layers are dependent on the particular properties required at various locations within the sound transmitter.

in some sound transmitters additional cavities are provided contiguous to the openings for the microphones particularly at the positions of the sound inlet or outlet openings.

With the microphones disposed interiorly of the housing, it is important that the sound be able to reach them and, accordingly, the housing is made permeable, that is, it is provided with openings or a material is used which permits sound to pass through thehousing and reach themicrophones. Ac-

cordingly, the housing may be formed from a perforated sheet metal, a die cast metal, or a plastic material which is constructed of intersecting webs affording a plurality of openings through which sound may pass. Preferably the housings are provided with a support means of some type, such as a plug connection or some other mechanical device.

As indicated earlier, the pore size. of the open cell foam material can be during manufacture to accommodate the particular conditions experienced. For use within a sound transmitter housing, the foam material is selected so that its pore size will not absorb sound waves to any appreciable degree within the audible range of the human ear. Foam materials having between 36 to 64 pores per square centimeter or 216 to 512 pores per cubic centimeter have proved to be particularly satisfactory for the present invention. Where a thin layer is interposed between the microphone and remainder of the foam body, such a layer should have about to 315 pores per square centimeter or a 1660 to 5500 pores per cubic centimeter. Other layers of foam material may be used to produce special effects within the sound transmitter;

To gain the full benefits of the foam material, there should be no rigid mechanical parts extending. exteriorly from the body of foam. The only connection extending from within the housing isthe electric lead. However, since a flexible electric lead can be supplied the lead does notadversely effect the dampening of the vibrations by the foam material.

By using foam material as a cushion for the various transducer parts within a D, transmitter housing, a number of advantages are gained though only a relatively small expenditure is for required the cushioning material.

Accordingly, the primary object of the present invention is to utilize a foam material to support and protect the elements within a sound transmitter housing from the adverse effects of wind and shock. 7

Another object of the invention is to provide a body of foam material into which the various transmitter elements can be assembled and then inserted into-the sound transmitter houssertion into the housing.

A further object of the invention is to provide adequate protection for the elements within the sound transmitter from both shock and wind and to do so in a relatively inexpensive manner.

Moreover, another object of the invention is to achieve a sound transmitter construction which can be easily and economically packaged and is adequately protected against shock in rough handling or in transit. Since the transmitter elements are internally supported within the housing the unit may be packaged in a simple cardboard box or similar container which conforms to the shape of the unit.

Another object of the invention is to supply openings through vthe transmitter housing to admit sound to the microphone enclosed by the foam material.

Another object of the invention is to provide a body of foam material made up of different layers, each layer having distinct characteristics determinable by the position 'of the layer within the housing.

Still, a further object of the invention is to use an open cell polyurethane foam which is inexpensive and easy to shape for use as the support material within the sound transmitter hous- 5 ing.

Yet, a further object of the invention is to provide an effective, efficient and economical means for protecting moving coil microphones from the effect of wind and shock.

Therefore, the present invention is directed to an open cell foam-type material for use in a sound transmitter housing to protect the transducing means from the effects of shock and wind. The housing is provided with openings or other means through which sound can pass to the transducing means. The foam material completely encloses the transducing means cushioning it from any shock transmitted through the housing and also affording a dampening effect for any vibrations generated within the housing. Additionally, the foam material, as an unitary or composite element encloses the transducing means, forming an assembly which can be inserted into the housing in a simple and efficient operation. Moreover, the foam material can be made in a multilayer construction with the various layers having special characteristics to accommodate the particular requirement of certain microphones.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings:

- FIG. la is a view, partly in section, of one embodiment of the present invention;

FIG. lb is an exterior side view of the embodiment shown in 1a with certain interior portions shown dotted;

FIG. lc'is an end view of the embodiment shown in FIG. 1a also having certain of the interior portions shown dotted;

FIG. 2 is an axonometric view of another embodiment of the present invention;

FIG. 3 shows an articulated joint construction for still another embodiment of the present invention;

FIG. 4 is a schematic sectional view of yet another embodiment of the present invention;

FIG. 5 is an exterior view of a further embodiment of the present invention;

FIG. 6 is a cross-sectional view showing an alternative interior construction for the embodiment shown in FIG. 1;

FIG. 7 is a cross-sectional view of another embodiment of the present invention incorporating a multilayered support construction; and

FIG. 8 is a perspective view of another embodiment of the invention provided with a special wind cap.

DETAILED DESCRIPTION Three separate views of a sound transmitter A are set forth in FIGS. 1a, lb and 1c. The sound transmitter A is a two-channel, cardioid pattern, microphone assembly comprising a treble microphone 1 and a bass microphone 2. As seen in FIG. la, the microphones are arranged in side-by-side relationship, depending on the orientation of the sound transmitter A in its working position, the microphones may be disposed either side-by-side or one arranged above the other. A body 6 of open cell foam material is disposed within the sound transmitter A and contains a pair of recesses 3 and 4 which receive the

microphones

1 and 2. The recesses 3 and 4 are shaped to hold the microphones, and having the same cylindrical shape. In FIG. la, the sound transmitter is composed of a number of parts and the body 6 comprises two

parts

6a, 6b divided by a parting plane or joint 5 which bisects the recesses 3 and 43 (see FIGS. lb and 10). Accordingly, the-recesses 3 and 4 form semicylinders in the parts 601 and 6b.

In additionto the microphones l and 2, the sound transmitter A contains several circuit elements 7 arranged rearwardly of microphone 1 (FIG. la), however, these elements, though shown dotted in FIG. lb, are not shown in FIG. Ic. In order to accommodate the circuit elements 7, additional recesses 8 are provided in the body of. foam material. As can be seen in FIG. 1b, the joint 5 also divides the recesses 8 into two separate openings. In assembling the sound transmitter, the microphones l and 2 and circuit elements 7 are placed within the lower portion 6b of the body 6 of the foam material and then the upper portion be, as viewed in FIG. lb, is placed on top and the assembly is ready to be inserted into the transmitter with the parts held in position by the foam material. Since the foam material is porous, it can directly contact the microphones. Though the electricalterminals to the sound transmitter circuit elements are not shown, the flexible electrical leads 9 are indicated in FIG. 1a. Viewing FIGS. 1a, lb and Ic, it will be readily apparent that the body 6 of foam material positions and supports the various sound transmitter elements and the structural parts, previously required to mount and protect elements, are no longer needed. Though shown separately in the drawings, the

microphones

1 and 2 may be mechanically interconnected for storage purposes.

Though the body 6 of open cell foam material adequately contains the sound transmitter elements, a housing MP is necessary to protect the foam material from rough handling. Since the

microphones

1 and 2 are disposed interiorly of the housing and surrounded by the foam material, it is necessary that the housing be sufficiently permeable to sound so that it will reach the sound inlet openings of the microphones l and 2. The housing It) may be constructed of perforated sheet iron having a plurality of openings 10a for admitting sound into the housing. In addition to sheet iron, other materials could be employed for the housing, such as plastics formed in interconnected webs providing the openings for the passage of sound into the housing.

Since the housing 10 is a geometrical body, its shape does not inherently define its orientation for use and it is preferable if its working position is idenfified in some manner. For this purpose, the openings 10a may be arranged so that they identify the position of the microphone sound inlet openings within the housing 10, or a different pattern may be provided for the material forming the housing surface in the location of sound openings. Another identifying means would be a color dot or similar mark for distinguishing the portion of the housing through which sound reaches the microphones.

In FIG. 2, another sound transmitter B is shown having a rectangular box-shaped housing 10. The housing It) is provided with a plurality of openings 10'd at one end for identifying the sound inlet portion of the transmitter.

Another arrangement for identifying the sound inlet section is shown in FIG. 3 wherein the sound transmitter C comprises a housing 10" having a plurality of circular openings 10"a at one end. Located at the sound inlet section of the housing 10' is an articulated support member 22 having an arm 23 for connection to a stand or some other structure (not shown) for orienting the transmitter in its proper position. In addition to the embodiments shown in FIGS. 2 and 3 a handle could be attached to the transmitter housing or some other means provided for affixing the transmitter to a support which would readily identify the sound inlet section of the housing.

In FIG. 4 a sound transmitter D is without its housing. In this transmitter D, the individual microphones are arranged in axial alignment, with the treble microphone 11 disposed in front of the bass microphone I2. Laterally enclosing the microphones I1 and I2 is a body 13 of open cell foam material for supporting and positioning the microphones. If the body consists of a single piece of material, a cylindrical opening or hole 13a is provided for the microphones. When the microphones are positioned within the hole 13a, a disc of foam material is disposed between them and a pair of discs or plugs 13b close off the ends of the hole 13a so that the microphones are completely embedded in the foam material. Alternatively, if the body 13 of foam material is divided into two parts, similar to the arrangement shown in FIGS. la, lb and is, it would not be necessary to provide the

discs

13c, 13b which separate the microphones and close up the ends of the cylindrical hole 13a.

The sound transmitter D, shown in FIG. 4, in which the microphones are arranged in axial alignment could be incorporated into a housing 30, such as shown in FIG. 5. For purposes of this invention, it is not important whether the housing 30 is perforated throughout its entire surface or, as shown in the drawings, is provided with a cap 24 having slotted openings at one end and a plurality of perforations or openings 25 at its opposite end.

In instances where special acoustic properties are desired for the microphones, the foam body which encloses the microphones may be provided with additional cavities located about or at the sound openings of the microphones. In FIG. 6, an arrangement is shown, similar to that in FIG. 1a, where the sound transmitter A has a number of cavities or openings provided in the body 6' of open cell foam material at the sound inlet openings of the microphones l and 2'. Three cavities M are provided about the microphone l with one of the cavities communicating between the two microphones. Additionally, two cavities are located at one end of the microphone 2 and another cavity I6 is situated at is other end. These cavities improve the coupling between the body 6' of foam material and the microphones l, 2' so that the acoustic properties of the sound transmitter A are improved. Since the cavities 1d, 15, I6 are provided for the improvement of the acoustical properties of the microphone l and 2' there is no need for such cavities disposed about the circuit element 7'.

For particularly effective protection from shock and wind the body of open cell foam may be formed in a plurality of layers with each layer having a different pore size. A multilayered construction of the foam material is shown in FIG. 7 where the microphone 17 is positioned within three layers I8, 19, of the foam material. The inner layer 18 has relatively small pores and a high degree of elasticity for resiliently holding the microphone. The intermediate layer 19 is considerably thicker and has much larger pores and the outer layer 29 is, like the inner layer 18, quite thin and has small pores. Electrical leads 31 extend through the layers of foam to the exterior of the transmitter E. a

In instances where additional protection is required from strong winds, the arrangement shown in FIG. 8 is preferable since it provides an outer wind screen formed by cap 26 around the sound inlet section of the sound transmitter F. The cap 26 is cylindrical in form and contains a body of open cell foam material 27 which supplies the additional screen about the sound inlet end of the housing 21. While the cap 26 may be required in cases where the sound transmitter F is exposed to a strong wind, under normal conditions the arrangement of the foam wifliin the housing is suflicient to suppress any noises due to the wind.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understoodthat the invention may be embodied otherwise without departing from such principles.

We claim:

1. A sound transmitter housing comprises rigid walls forming an exterior casing which is permeable to sound at least in part, transducing means positioned within and spaced inwardly from said walls and having the sound inlet openings thereto oriented to receive sound passing through said walls, and a body of open cell foam-type polyester material completely embedding said transducing means and filling the open spaces within the casing between said transducing means and the interior of said walls, said foam-type material disposed in contacting relationship with said transducing means and said walls so that a continuously extending body of said foamtype material is positioned between the part of said casing permeable to sound and the sound inlet openings of said transducing means for forming wind screen and for holding said transducing means in position, said open cell foam-type material having a pore size which will not absorb sound waves to any appreciable degree within the audible range of the human ear, said foam-type material forming a packagelike assembly for receiving said transducing means so that the packagelike assembly can be inserted as a unit into said casing whereby said transducing means are internally supported within said casing.

2. A sound transmitter housing, as set forth in claim 1, wherein said foam-type material is molded and has recesses shaped to match the configuration of said transducing means positioned within said casing.

3. A sound transmitter housing, as set forth in claim 2, wherein said foam-type material is comprised of a one-piece main part for the embedment of said transducing means and shaped in sections of said foam-type material for filling the remainder of the openings not filled by said transducing means.

4. A sound transmitter housing, as set forth in claim 2, wherein the said foam-type material is comprised of at least two molded sections having recesses therein shaped to receive said transducing means and said molded sections having a dividing plane therebetween which passes through the recesses for facilitating the assembly of said transducing means therein.

5. A sound transmitter housing, as set forth in claim 4, wherein the molded sections of said foam-type material has recesses shaped therein accessible from the exterior of said molded sections.

6. A sound transmitter housing, as set forth in claim 2, wherein said molded open cell foam-type material comprises at least an inner layer of foam-type material which is disposed in contact with and completely encloses said transducing means and has a high degree of elasticity for resiliently holding said transducing means, and an outer layer of open cell foamtype material completely enclosing said inner layer and the open cells in said outer layer being larger than the open cells in said inner layer.