CARDIOID MICROPHONE

• US 3,585,317 A
• Filed: 01/04/1968
• Issued: 06/15/1971
• Est. Priority Date: 01/04/1968
• Status: Expired due to Term

• Current Assignee: Alexander L. Dvorsky
• Original Assignee: Alexander L. Dvorsky
• Inventors: Dvorsky, Alexander L.
• Application Number:
  US04/695,613
• Time in Patent Office: 1,258 Days
• US Class Current: 381/368
• CPC Class Codes: H04R 1/38 in which sound waves act upon both sides of a diaphragm and incorporating acoustic phase-shifting means, e.g. pressure-gradient microphone
• CPC Class Codes: H04R 7/26 Damping by means acting directly on free portion of diaphragm or cone air damping H04R1/28

Abstract

Directional (cardioid) response is achieved by acoustical phase shift through porous plates and slots which are adjustable. Rubber vibration isolator means adjustably secures the transducer in the housing. A multipath acoustical system, combined with a high-compliance diaphragm, insures improved response and greater discrimination over a wide frequency range.

Claims

1. A directional microphone of the cardioid type, having one side of its diaphragm exposed directly to sound waves in air, and having the other side of the diaphragm closed off from direct contact with said sound waves by an acoustic delay path leading partly through A controlled distance in porous material and partly through an open slot at an edge of said porous material, said delay path being divided into parallel courses and said porous material and said slot are both made plural so that at least one portion of said material and one of said slots exist in each of said parallel courses, the portions of porous material in said parallel courses being of different density.

2. A directional microphone of the cardioid type, having one side of its acoustic diaphragm exposed directly to sound waves in air, and having the other side of its diaphragm closed off from direct contact with said sound waves by an acoustic delay path which is divided into parallel courses, each course leading partly through a controlled distance in porous material and partly through an open slot at an edge of said porous material, said slot providing a partial bypass around said porous material.

3. The microphone of claim 2, further characterized in that each said delay path is branched after leading through said porous material and said slot, with a first branch communicating with said other diaphragm side and with a second branch communicating with a damped resonance cavity.

4. The microphone of claim 3, in which said first branch includes a restriction through which sound waves pass before communicating with said other diaphragm side, and said second branch includes a restriction through which sound waves pass before communicating with said resonance cavity.

5. A microphone comprising a tubular body, a wall formed of medium soft rubber overlying an opening into said tubular body and resiliently supporting a transducer unit, said body having an inner ledge spaced from its opening, and a link member having opposite ends respectively connected to said rubber wall and said ledge, the connection between said link member and said ledge being adjustable and disposed so that a pulling force may be applied to said link member to seat said rubber wall in the surface defining said body opening with a selected force.

6. The construction of claim 5, wherein said transducer unit is supported on that surface of the rubber wall which is directed outwardly of said tubular body, means mounting an acoustic diaphragm adjacent to said transducer unit, and a passage effecting acoustic communication between the rear surface of the diaphragm and the interior of said tubular body.

7. A resilient mounting for securing a transducer in its protective casing, comprising a cuplike resilient body of substantial volume having a recess on one side for receiving said transducer, a radial flange integral with said body and resting on an edge of said casing, means to adjustably urge said transducer into said body without compressing said body, said means to urge also applying shear stress between said flange and said edge.