Electro-acoustic transducer housing adapted for telephonic pcm communication systems

Claim 2

In an electroacoustic transducer housing including a cover with holes therein, a transducer capsule having a face and containing an electroacoustic transducer and having apertures in the face thereof, the improvement comprising a first, central cavity formed by said face of said transducer capsule and said cover, said first cavity coupling said apertures of said transducer acoustically to the exterior through said cavity and said holes in said cover, a second cavity formed by said cover and the periphery of said face of said capsule comprising a Helmholtz resonator for absorbing sound at its resonant frequency connected with said first cavity by means of an aperture formed by and between said cover and said face.

Claim 3

Apparatus in accordance with claim 1 wherein said second cavity and said aperture are ring-shaped.

Claim 4

Apparatus in accordance with claim 1 wherein said second cavity and said aperture have the shape of concentric rings.

Claim 5

Apparatus in accordance with claim 1 wherein said cover is shaped circularly and serves to keep an electro-acoustic transducer in its position, said cover including two ring-shaped protrusions and a ring-shaped recess between them, the outer one of said ring-shaped protrusions being so structured to rest tightly on said capsule so that a narrow channel Remains between the inner one of said inner ring-shaped protrusions and said capsule, said channel forming the aperture of said Helmholtz resonator, and said cavity for said Helmholtz resonator being formed by said ring-shaped recess.

Claim 6

Apparatus in accordance with claim 4 wherein said inner ring-shaped protrusion is structured for positioning opposite said holes of said capsule of said electro-acoustic transducer.

Claim 7

Apparatus in accordance with claim 1 comprising a telephone apparatus of a communication system in which voice signals are transmitted in PCM coding, characterized in that the resonant frequency of said Helmholtz resonator is substantially at least equal to one-half of the PCM sampling frequency.

Claim 8

In a housing including a cover having sound holes therein, a transducer capsule containing an electro-acoustic transducer, said capsule having a face including an opening connecting said transducer acoustically therethrough, the improvement comprising said cover including on its inside surface a recess forming in combination with said face of said capsule a resonant cavity having a restricted entrance for absorbing audible acoustic energy, said restricted entrance comprising an aperture formed between said face and said cover said aperture and said opening in said capsule being in close proximity said cover and said face forming a central cavity communicating between said opening in said face and said sound holes.

Claim 9

In a housing including a cover having sound holes therein, a transducer capsule containing an electro-acoustic transducer, said capsule having a face including an opening connecting said transducer acoustically therethrough, the improvement comprising said cover including on its inside surface a recess forming in combination with said face of said capsule a resonant cavity having a restricted entrance for absorbing audible acoustic energy, said restricted entrance comprising an aperture formed between said face and said cover said aperture and said opening in said capsule being in close proximity said cover and said face forming a central cavity communicating between said opening in said face and said sound holes.