Electret earphone

Claim 2

An electroacoustic transducer comprising: a thin, substantially flexible electrically conductive diaphragm; a pair of rigid backplates positioned on opposite sides of said diaphragm; a separate imperforate electret bonded to each said backplate along the surface thereof confronting said diaphragm, each said electret being imperforate to provide a single continuous surface uninterrupted by perforations, thereby to maximize the ratio of surface area of perimeter length; each said backplate being vented at locations not obstructed by the electret bonded thereto; said diaphragm and each of said electrets being electrically insulated from one another; means for supporting said diaphragm between said electrets with sufficient clearance for said diaphragm to vibrate; and means for electrically connecting individually to said diaphragm and to each of said electrets.

Claim 3

An electroacoustic transducer as defined in claim 1, wherein said electrets are substantially circular.

Claim 4

An electroacoustic transducer as defined in claim 1, wherein said device is a receiver.

Claim 5

An electroacoustic receiver as defined in claim 3, wherein said device is an earphone.

Claim 6

An electroacoustic receiver comprising: a thin, substantially flexible electrically conductive diaphragm; a pair of rigid electrode backplates positioned on opposite sides of said diaphragm; a separate imperforate electret bonded to and covering a portion of each of said electrode backplates along the surface thereof confronting said diaphragm, each said electret being imperforate to provide a single continuous surface uninterrupted by perforations, thereby to maximize the ratio of surface area to perimeter length; each of said imperforate electrets being substantially planar and having a ratio of the longest line along the surface which would pass through the center of gravity to the shortest line along the surface which would pass through the center of gravity not exceeding three; each said electrode backplate being vented for acoustic airflow at locations not obstructed by the electret bonded thereto; said diaphragm and each of said electrets being electrically insulated from one another; means for supporting said diaphragm between said electrets with sufficient clearance for said diaphragm to vibrate; and means for electrically connecting individually to said diaphragm and to each of said electrets.

Claim 7

An electroacoustic receiver comprising: a thin, substantially flexible electrically conductive diaphragm; a pair of rigid electrode backplates positioned on opposite sides of said diaphragm; a separate imperforate electret bonded to and covering a portion of each of said electrode backplates along the surface thereof confronting said diaphragm, each said electret being imperforate to provide a single continuous surface uninterrupted by perforations, thereby to maximize the ratio of surface area to perimeter length; each of said imperforate electrets being substantially planar and having a ratio of the longest line along the surface which would pass through the center of gravity to the shortest line along the surface which would pass through the center of gravity not exceeding three; each said electrode backplate being vented for acoustic airflow at locations not obstructed by the electret bonded thereto; said diaphragm and each of said electrets being electrically insulated from one another; means for supporting said diaphragm between said electrets with sufficient clearance for said diaphragm to vibrate; and means for electrically connecting individually to said diaphragm and to each of said electrets.

Claim 8

An electroacoustic receiver as defined in claim 5, wherein said electrets are substantially circular.

Claim 9

An electroacoustic receiver as defined in claim 5, wherein said device is an earphone.

Claim 10

A hearing aid comprising: microphone means; amplifier means; push-pull driving means; an electrostatic receiver comprising: a casing; acoustic ports; a thin, substantially flexible electrically conductive diaphragm; a pair of rigid backplates positioned on opposite sides of said diaphragm; a separate imperforate electret, each said electret being imperforate to provide a single continuous surface uninterrupted by perforations, thereby to maximize the ratio of surface area to perimeter length; said backplates being vented at locations not obstructed by said electrets; said diaphragm and each of said electrets being electrically insulated from one another; means for supporting said diaphragm between said electrets with sufficient clearance for said diaphragm to vibrate; and means for electrically connecting individually to said diaphragm and to each of said electrets.

Claim 11

A hearing aid comprising: microphone means; amplifier means; push-pull driving means; an electrostatic receiver comprising: a casing; acoustic ports; a thin, substantially flexible electrically conductive diaphragm; a pair of rigid backplates positioned on opposite sides of said diaphragm; a separate imperforate electret, each said electret being imperforate to provide a single continuous surface uninterrupted by perforations, thereby to maximize the ratio of surface area to perimeter length; said backplates being vented at locations not obstructed by said electrets; said diaphragm and each of said electrets being electrically insulated from one another; means for supporting said diaphragm between said electrets with sufficient clearance for said diaphragm to vibrate; and means for electrically connecting individually to said diaphragm and to each of said electrets.

Claim 12

An electroacoustic transducer comprising: an electrically conductive vibratile diaphragm; a pair of rigid backplates positioned on opposite sides of said diaphragm, said backplates having plastic bases with an electrically conductive coating thereon, said coating not exceeding one micron in thickness; a separate imperforate electret bonded to each said backplate along the surface thereof confronting said diaphragm, each electret comprising an electrically non-conductive member having thermal expansion characteristics similar to the thermal expansion characteristics of said base and being imperforate to provide a single continuous surface uninterrupted by perforations, thereby to maximize the ratio of surface area to perimeter length, an obverse surface of said member confronting said diaphragm, an electrically conductive backing on the reverse surface of said member, said backing bonding said member to said backplate in surface to surface contact, each said electret and its associated backplate having similar thermal expansion characteristics; each said backplate being vented at locations not obstructed by the electret bonded thereto; said diaphragm and each of said electrets being electrically insulated from one another; means for supporting said diaphragm between said electrets with sufficient clearance for said diaphragm to vibrate; and means for electrically connecting individually to said diaphragm and to each of said electrets.

Claim 13

An electroacoustic transducer comprising: an electrically conductive vibratile diaphragm; a pair of rigid backplates positioned on opposite sides of said diaphragm, said backplates having plastic bases with an electrically conductive coating thereon, said coating not exceeding one micron in thickness; a separate imperforate electret bonded to each said backplate along the surface thereof confronting said diaphragm, each electret comprising an electrically non-conductive member having thermal expansion characteristics similar to the thermal expansion characteristics of said base and being imperforate to provide a single continuous surface uninterrupted by perforations, thereby to maximize the ratio of surface area to perimeter length, an obverse surface of said member confronting said diaphragm, an electrically conductive backing on the reverse surface of said member, said backing bonding said member to said backplate in surface to surface contact, each said electret and its associated backplate having similar thermal expansion characteristics; each said backplate being vented at locations not obstructed by the electret bonded thereto; said diaphragm and each of said electrets being electrically insulated from one another; means for supporting said diaphragm between said electrets with sufficient clearance for said diaphragm to vibrate; and means for electrically connecting individually to said diaphragm and to each of said electrets.

Claim 14

An electroacoustic transducer as defined in claim 9 wherein said electrically conductive surface of said electret does not exceed 0.15 microns in thickness.

Claim 15

An electroacoustic transducer comprising: a closed container; a thin, substantially flexible electrically conductive diaphragm mounted at its perimeter inside said container, thereby dividing said container into two sections; a pair of rigid backplates mounted inside said container on opposite sides of said diaphragm with sufficient clearance for said diaphragm to vibrate, each said backplate together with the walls of said container forming an acoustic chamber; a separate imperforate electret bonded to each said backplate along the central portion of the surface thereof confronting said diaphragm; said backplate having holes through it at locations surrounding said electret for providing acoustic passageways between said diaphragm and said acoustic chambers; and an opening in said container for providing an acoustic port communicating with at least one of said acoustic chambers.

Claim 16

An electroacoustic transducer comprising: a closed container; a thin, substantially flexible electrically conductive diaphragm mounted at its perimeter inside said container, thereby dividing said container into two sections; a pair of rigid backplates mounted inside said container on opposite sides of said diaphragm with sufficient clearance for said diaphragm to vibrate, each said backplate together with the walls of said container forming an acoustic chamber; a separate imperforate electret bonded to each said backplate along the central portion of the surface thereof confronting said diaphragm; said backplate having holes through it at locations surrounding said electret for providing acoustic passageways between said diaphragm and said acoustic chambers; and an opening in said container for providing an acoustic port communicating with at least one of said acoustic chambers.