Reversible anti-noise microphone

• US 4,009,355 A
• Filed: 07/02/1975
• Issued: 02/22/1977
• Est. Priority Date: 07/02/1975
• Status: Expired due to Term

• Current Assignee: Roanwell Corp.
• Original Assignee: Roanwell Corp.
• Inventors: Poradowski, Lech M.
• Primary Examiner(s): Stellar, George G.
• Application Number:
  US05/592,632
• Time in Patent Office: 601 Days
• Field of Search: 179/1 D, 179/146 R, 179/107 FD, 179/121 R, 179/121 D, 179/138 R, 179/138 VL, 179/178, 179/179, 179/180, 174/52 R, 325/119
• US Class Current: 381/358
• 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

Abstract

This microphone has two opposed faces. The sound to be picked up may be directed toward either one of the two opposed faces with equivalent electrical output from the microphone in either case. Since background noise impinges equally on both of the two opposed faces, its effect on the microphone diaphragm is self-canceling, and causes substantially zero output from the transducer.

Claims

1. A reversible anti-noise microphone, including:

a. a housing comprising two identical parts, each part including;

1. a peripheral wall; and

2. a transverse wall, each said transverse wall defining a face of the housing;

b. means fastening the housing parts together with said peripheral walls abutting and said transverse walls spaced apart and forming first and second opposite faces with at least one sound transmitting opening in each face;

c. a transducer enclosed in the housing including a diaphragm having opposite surfaces;

d. means defining a first acoustical path providing communication between the opening in the first face of the housing and a first surface of said diaphragm;

e. means defining a second acoustical path providing communication between the opening in the second face of the housing and a second surface of the diaphragm, said first path being acoustically longer than the second path;

f. first acoustical resistance means in the first path; and

g. second acoustical resistance means in the second path, said second acoustical resistance means having a greater acoustical loss than the first acoustical resistance means, the losses being inversely related to the lengths of said paths so that the frequency response curves of the two paths are substantially the same.

2. A microphone as in claim 1, in which each of the two housing parts includes first and second transverse septums separating the interior of the housing part into three recesses;

a. said peripheral wall including a first section having a part-cylindrical inner face greater than a semi-cylinder and second and third sections having flat inner surfaces extending tangentially from the first section and converging to an end section;

b. said first transverse septum having a part-cylindrical surface cooperating with the inner face of said first wall section to define a first of said three recesses, said transducer being received in said first recess;

c. said second transverse septum extending between said second and third wall sections and cooperating therewith and with said first transverse septum to define a second recess;

d. said second transverse septum cooperating with said second and third wall sections and said end section to define a third recess for receiving a conduit anchor, said end section having a passage therein for receiving a conduit;

e. said second transverse septum having a notch for receiving two wires from said conduit;

f. said first transverse septum having a notch at each end for receiving a wire from said conduit; and

g. said first and second transverse septums cooperating with said notches to define tortuous strain relieving passages for said wires.

3. A microphone including:

a. a housing comprising;

1. two abutting parts of similar form, said housing having two opposed faces, at least one face having a sound transmitting opening therein, each said housing part including;

i. a peripheral wall, and a transverse wall, each transverse wall defining a face of the housing; and

ii. means fastening the housing parts together with the peripheral walls abutting;

b. a transducer in the housing including two electrical terminals, and a diaphragm upon which sound passing through the opening impinges;

c. each of the two housing parts including first and second transverse septums;

d. each said peripheral wall including a first section having a part-cylindrical inner face greater than a semi-cylinder and second and third sections having flat inner surfaces extending tangentially from the first section and converging to an end section;

e. said first transverse septums having part-cylindrical surfaces cooperating with the inner faces of said first wall sections to define a cylindrical recess receiving the transducer;

f. said second transverse septums extending between said second and third wall sections and cooperating therewith and with said first transverse septums to define a second recess;

g. said second transverse septums cooperating with said end sections and said second and third wall sections to define a third recess receiving a conduit anchor, said end sections having cooperating notches defining a passage therein receiving a conduit;

h. said second transverse septums having opposed notches receiving wires extending from said conduit;

i. said first transverse septums having opposed notches at each end, each pair of opposed notches receiving a wire from said conduit; and

j. said first and second transverse septums cooperating with said notches to define tortuous strain relieving passages for said wires.

4. A microphone as in claim 3, in which said fastening means comprises a locating pin projecting from the abutting surface of the peripheral wall at a point spaced from the longitudinal axis of the housing part, and a recess in said abutting surface for receiving a similar locating pin, said recess being located at a point spaced from the longitudinal axis of the housing part on the opposite side thereof from said locating pin, said pin and recess being symmetrically spaced.