US 3862377 A
A microphone stand for responding to the floor wave of a distant acoustical source which utilizes a body of open cellular foam plastic having between 10 and 80 voids per linear inch and having a total volume of voids of at least 90 percent of the total volume of the body. The body has a flat side which permits it to be placed upon a horizontal surface such as a floor and a cavity therein to snugly accommodate a microphone and hold it in position.
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Description (OCR text may contain errors)
States Patent [191 Burroughs FLOOR WAVE MICROPHONE STAND  Inventor: Louis Burroughs, Lake l-lavasu,
 Assignee: Electro-Voice, Incorporated,
 Filed: May 29, 1973  Appl. No.: 364,309
 US. Cl. 179/146 R, 179/184  Int. Cl H04r 1/02  Field of Search 179/146 R, 147, 184
 References Cited UNITED STATES PATENTS Gorike 179/184 Jan. 21, 1975 Primary ExaminerWilliam C. Cooper  ABSTRACT A microphone stand for responding to the floor wave of a distant acoustical source which utilizes a body of open cellular foam plastic having between 10 and 80 voids per linear inch and having a total volume of voids of at least 90 percent of the total volume of the body. The body has a flat side which permits it to be placed upon a horizontal surface such as a floor and a cavity therein to snugly accommodate a microphone and hold it in position.
4 Claims, 4 Drawing Figures FLOOR WAVE MICROPHONE STAND The present invention relates generally to microphone stands, that is, support structures for mounting a microphone in position to respond to acoustical energy. More specifically, the present invention relates to microphone stands for use in positioning microphones for responding to acoustical energy originating at a substantial distance from the microphone.
Microphone stands are well known in the art and generally consist of a base adapted to be positioned upon a horizontal surface, usually a floor or table, a stern extending from the base generally perpendicular to the horizontal surface, and a clamping structure for securing the stem to the microphone itself. Often the microphone is removable from the clamp, and often the stand includes a compliant structure between the stern and the microphone for isolating the microphone from mechanical vibrations derived from the base. In addition to the stationary stands of the type described above, microphones are often mounted for movement on a boom, and such devices include a mechanical means for moving the clamp and microphone with respect to the base, and in some cases for moving the base with respect to the horizontal surface.
Most microphone stands mount the microphone at a considerable distance from the horizontal surface, often four or five feet. Stands for mounting a microphone on a table, however, may position the microphone a few inches above the surface of the table. The present inventor has recognized that such microphones may be positioned on the floor to respond to acoustical energy originating at a substantial distance, and the microphone will respond primarily to the floor wave of that acoustical energy.
Acoustical energy originating at a distance above the floor of a room, for example 3 feet, and at a substantial distance from the microphone, for example to feet, will produce reflections from the floor which are received by a microphone mounted above the floor level. Since sound waves travel from the point of origin outwardly in all directions at a uniform rate, those sound waves reaching the microphone after reflection from the floor travel a further distance than the sound waves which travel directly from the source to the microphone. Accordingly, there is a phase difference between the sound wave which travels directly from the source to the microphone and the sound wave which is reflected from the floor to the microphone. Accordingly, the floor wave of the acoustical energy, that is, the acoustical energy from a distant source which may be detected at a few inches above the floor, contains the direct wave from the sound source and only those waves which are reflected immediately in front of the microphone, and hence, the floor wave does not contain acoustical energy substantially out of phase with the direct sound wave from the source. The Apr., 1971 issue of DB Magazine contains an article entitled A Distant Micing (sic) Technique by Anderson and Schuelin which describes a microphone stand designed specifically for the purpose of positioning a microphone to respond to the floor wave from a distant source.
While the acoustical conditions adjacent to the floor with respect to a distant source are different than the acoustical conditions at a significant distance above the floor, it is also true that the environmental conditions at floor level differ from those above the floor level. Depending upon the precise location, microphones mounted adjacent to the floor are subjected to larger quantities of dust, dirt, air drafts or winds, and are in closer proximity to shocks and vibrations transmitted from the floor. It is an object of the present invention to provide a microphone stand for positioning a microphone adjacent to the floor to respond to the floor wave of a distant source which protects the microphone against dust, dirt, wind noises, and minimizes the effects of shock and vibration.
Further, it is an object of the present invention to provide a microphone stand which will permit the microphone to be positioned very close to the floor and yet maintain shock and vibration isolation, protection against dust, dirt and wind noises.
In addition to these objects, it is an object of the present invention to provide a very inexpensive and durable microphone stand, and a microphone stand which may readily be removed from the microphone to permit the microphone to be used as ahand held microphone or mounted on a conventional stand.
The inventor has found that a microphone stand for responding to the floor wave of a distant acoustical source and achieving the foregoing objects may consist of a body of open cellular foam plastic with cell sizes sufficiently large to permit the passage of sound but of insufficient size to permit ready passage of dust and dirt, this body having a flat side which may be positioned on the floor and a cavity therein for containing a microphone. The inventor has found that the cavity is preferably in the form of a recess from the flat side of the foam body to permit ready installation and removal of the microphone. The foam plastic should be compliant to dampen shock and vibrations present on the floor structure.
The invention will be more thoroughly described with reference to the accompanying drawings, in which:
FIG. 1 is an elongated sectional view of a microphone stand constructed according to the present invention including a microphone mounted therein;
FIG. 2 is a bottom view of the microphone stand of FIG. 1, the microphone having been removed;
FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2; and
FIG. 4 is a side elevational view of the microphone stand of FIGS. 1 through 3.
FIG. 1 shows a microphone 10 mounted within a body of foam plastic 12 which constitutes the microphone stand. The body l2 has a flat surface 14 which is adapted to be positioned on a floor, or may be positioned on a table if desired. The body has an axis disposed in the surface 14 parallel to the axis of elongation of the body 12, this axis being located at 16 in' FIGS. 2 and 3, and the body 12 is semi-cylindrical with respect to the axis 16. The body 12 has a forward end 18 and a rearward end 20, and these ends are quarter spheres .with respect to centers located in the flat surface 14 at the points 22 and 24 illustrated in FIG. 2. The radius of curvature of the quarter spherical ends 18 and 20 is the same as the radius of the semicylindrical portion of the body 12. I
A circular recess 26 extends into the body 12 concentrically about an axis normal to the surface 14 at the center 16 of the quarter spherical end 18 of the body. The recess terminates in a semi-spherical dome 28 with a center 30, as illustrated in FIG. 3. The center 30 is located on the axis of the recess 26 and spaced from the center 16 on the flat surface 14 by a distance equal to the radius of the semi-spherical dome 28, thereby establishing the position of the microphone within the body 12 as will be hereinafter further explained. A cylindrical channel 32 extends parallel to the axis 16 from the recess 26 to an opening 34 in the quarter spherical end 20 of the body 12, the axis of the channel 32 passing through the center 30 of the semi-spherical dome 28.
The body 12 has been shaped to accommodate the microphone which has a cylindrical shank 36 with a diameter approximately equal to the diameter of the channel 34. The microphone 10 also has a generally spherical head 38 with a radius slightly less than the radius of the semi-spherical dome 28. The microphone is an omnidirectional microphone as illustrated but may also be a directional microphone since all portions of the microphone are subjected to the sound field through the foam body 12. Further, the microphone has a connector 40 disposed at its end opposite the head, and the connector 40 is removably connected to a cable 42.
The connector 40 and cable 42 are first disengaged to position the microphone 10 within the body 12. The cylindrical shank 36 of the microphone is then inserted into the channel 32 of the foam body 12 through the recess 26. The body 12 is constructed of sufficiently resilient material to permit the forward end 18 of the body to be distorted, and thus permit the cylindrical shank 36 of the microphone to be translated in the cylindrical channel 32 until the spherical head 38 of the microphone comes into abutment with the wall of the recess 26. The resilency of the material of the body 12 will thus permit the end 18 to resume its normal position, and the microphone will be positioned within the body as shown in FIG. 1. The cable 42 may then simply be affixed to the connector 40 of the microphone, the connector 40 protruding from the end of the body to permit connection.
The body 12 should be constructed of open cellular resilient foam plastic, and the cells should be sufficiently open to freely pass sound waves. It will be noted that the distance between the adjacent exterior surface of the body 12 and the spherical dome 28 is significantly less than the distance between other portions of the recess 26 and the exterior surface of the body 12 and may be as little as one-sixteenth inch, but no portion of the acoustical path to the head of the microphone should exceed 6 inches. This can only be accomplished without impairing the acoustical performance of the microphone by virtue of the fact that the open cellular foam material of the body is substantially transparent with respect to sound waves and does not provide a significant impedance to the passage of sound waves. In the particular embodiment described, the distance between the center of the semi-spherical dome 28 and the adjacent surface of the body 12 is approximately one-fourth inch, and this has been found to be satisfactory to protect the microphone against dirt and dust and to form an effective wind screen.
The open cellular foam material of the body may be the same type material utilized in wind screens, such as that disclosed in U.S. Pat. No. 3,236,328 of the present inventor entitled ACOUSTICAL DEVICE WITH PROTECTIVE SCREEN. The open foam cellular material should have between 10 and 80 cells per linear inch and at least 90 percent of the volume of the body 12 should constitute voids. Polyurethane foam has been found to meet these requirements.
The cylindrical head 38 of the microphone I0 is positioned as close to the flat surface 14 as possible without permitting the head 38 to contact the horizontal floor or other surface upon which the flat surface 14 of the body 12 rests. In the particular construction described, the head 38 of the microphone is spaced from the surface 14 by a distance of approximately one-fourth inch. Substantially all reflections from the floor resulting from a distant source of acoustical energy will arrive in phase with the acoustical energy arriving on a direct line from the source. However, the fact that reflections from the floor occuring near the microphone do arrive at the microphone, there will be a gain in microphone output up to about 6 decibels over the output of the microphone at a significant elevation from the floor.
The recess 26 and channel 32 are fabricated to accommodate the particular microphone 10 described in this embodiment. Other shaped recesses and channels may also be employed in the body 12 to accommodate different shaped microphones. Further, the exterior shape of the microphone may be varied, but it is desirable to provide at least three-eighths inch of foam plastic between those portions of the microphone that bear the weight of the microphone and the flat surface 14 for purposes of damping vibrations and shock.
The scope of the present invention is set forth in the accompanying claims, rather than the foregoing specification.
The invention claimed is:
l. A microphone and stand assembly comprising a body of open cellular foam plastic having between 10 and voids per linear inch and at least percent of its volume in voids, one side of said body being flat and adapted to rest upon a flat surface, said flat side having a recess extending therein, said recess terminating at a distance no less than one-sixteenth inch from the adjacent surface of the body, and a microphone disposed within the recess and supported by the body, the microphone being spaced from the plane of the flat surface of the body.
2. A microphone and stand assembly comprising the combination of claim 1 wherein the foam plastic of the body has a compliance at least equal to polyurethane.
3. A microphone and stand assembly comprising the combination of claim 1 wherein the microphone has a generally spherical head at one end and an elongated cylindrical shank extending therefrom, and the body has a semi-cylindrical portion centered on an axis disposed on the flat side of the body and quarter-spherical ends at opposite ends of the axis of a semi-cylindrical portion, said quarter-spherical end portions being centered on the axis of the semi-cylindrical portion, the recess being cylindrical with an axis passing through the center of the half spherical surface at one end of the body normal to the flat surface, said recess having a semi-spherical dome centered on the axis of the recess at a distance from the flat surface approximately equal to the radius of the half spherical dome, the channel extending from the recess parallel to the flat surface in alignment with the center of the semi-spherical dome, the shank of the microphone being snugly disposed in the channel and supporting the microphone within the body.
tance no less than one-sixteenth inch from the adjacent surface of the body, said cavity being adapted to accommodate the microphone and snugly fit at least a portion of the microphone to mount the microphone in a fixed position with respect to the body.