Membrane type electro-acoustic transducer

Claim 2

An electro-acoustic transducer comprising: (a) a magnetic circuit structure having at least one air gap; and (b) a vibrative structure disposed in said air gap; said vibrative structure comprising a frame member having at least one opening, a membrane fixed on said frame member so as to cover said opening, an acoustic-transparent member fixed on said frame member so as to form a space between said membrane and acoustic-transparent member, and an acoustic damping material disposed in said space in such a manner that said acoustic damping material smoothly contacts said membrane.

Claim 3

An electro-acoustic transducer as claimed in claim 1, wherein said acoustic-transparent member is a silk-mesh.

Claim 4

An electro-acoustic transducer as claimed in claim 1, wherein said frame member has front and back surfaces, said membrane is fixed to said front surface, said acoustic-transparent member is fixed to said back surface, and said acoustic damping material is disposed in a space between said front and back surfaces of said frame member.

Claim 5

An electro-acoustic transducer as claimed in claim 3, wherein said acoustic-transparent member is a silk-mesh and said acoustic damping material is made of urethane.

Claim 6

An electro-acoustic transducer as claimed in claim 3, wherein said membrane is a high molecular film.

Claim 7

An electro-acoustic transducer comprising: (a) a magnetic circuit including a pair of permanent magnets parallely positioned with each other; (b) a yoke magnetically coupled to said permanent magnets and having a center pole; (c) and a pair of pole plates magnetically coupled to said magnets, said center pole being positioned between said pole plates; (d) a pair of air gaps formed by said center pole and each of said pole plates, and (e) a vibrative structure disposed in said air gaps, said vibrative structure comprising a frame member positioned under said pole plates and having at least one opening, a membrane fixed on said frame so as to cover said opening, an acoustic-transparent member fixed on said frame so as to form a space between said membrane and acoustic-transparent member, and an acoustic damping material disposed in said space in such a manner that the acoustic damping material smoothly contacts said membrane.

Claim 8

An electro-acoustic transducer comprising: (a) a magnetic circuit including a pair of permanent magnets parallely positioned with each other; (b) a yoke magnetically coupled to said permanent magnets and having a center pole; (c) and a pair of pole plates magnetically coupled to said magnets, said center pole being positioned between said pole plates; (d) a pair of air gaps formed by said center pole and each of said pole plates, and (e) a vibrative structure disposed in said air gaps, said vibrative structure comprising a frame member positioned under said pole plates and having at least one opening, a membrane fixed on said frame so as to cover said opening, an acoustic-transparent member fixed on said frame so as to form a space between said membrane and acoustic-transparent member, and an acoustic damping material disposed in said space in such a manner that the acoustic damping material smoothly contacts said membrane.

Claim 9

An electro-acoustic transducer as claimed in claim 6, wherein said membrane has a conductor and said pole plates are positioned above said center pole, whereby a magnetic flux generated between said center pole and said pole plates crosses said conductor obliquely.