Acoustic transducer with improved low frequency response

Claim 2

An acoustic transducer comprising: a perforated member; a movable diaphragm spaced from said perforated member; spring means interconnecting said diaphragm and said perforated member for movably supporting said diaphragm relative to said perforated member; a pressure equalization slot for controlling the flow of fluid through said diaphragm; said slot equalizing the pressure on opposite sides of the diaphragm and having a width between 0.1 and 10μ for defining the low frequency response; and means for applying an electric field across said perforated member and said diaphragm for producing an output signal representative of the variation in capacitance induced by the variation of the space between said perforated member and said diaphragm in response to an incident acoustic signal.

Claim 3

The acoustic transducer of claim 1 in which a substantial portion of said slot is covered by said perforated member and said slot and perforations are unaligned to distort and lengthen the path of the fluid flow from said slot through said perforations.

Claim 4

The acoustic transducer of claim 1 in which said slot is disposed generally at the perimeter of said diaphragm.

Claim 5

The acoustic transducer of claim 3 in which said slot is approximately the length of the perimeter of said diaphragm.

Claim 6

The acoustic transducer of claim 1 in which said slot includes a plurality of sections.

Claim 7

The acoustic transducer of claim 1 in which said diaphragm is formed integrally with an insulator layer and said slot is formed at least partially between said conductive diaphragm and said insulator layer.

Claim 8

The acoustic transducer of claim 1 in which said slot is formed at least partially between portions of said conductive diaphragm.

Claim 9

The acoustic transducer of claim 1 in which said diaphragm, slot and spring means are made on a silicon wafer using micromachining photolithographic techniques.

Claim 10

The acoustic transducer of claim 1 in which said diaphragm and perforated member are made from a material from the group consisting of gold, nickel, iron, copper, silicon, polycrystalline silicon, silicon dioxide, silicon nitride, silicon carbide, titanium, chromium, platinum, palladium, aluminum and their alloys.

Claim 11

The acoustic transducer of claim 1 further including a filter spaced from said diaphragm for protecting said diaphragm from contaminants in the fluid.

Claim 12

An acoustic transducer comprising: a perforated member; a movable diaphragm spaced from said perforated member; spring means interconnecting said diaphragm and said perforated member for movably supporting said diaphragm relative to said perforated member; a pressure equalization slot for controlling the flow of fluid through said diaphragm; said slot equalizing the pressure on opposite sides of the diaphragm for defining the low frequency response; a substantial portion of said slot being covered by said perforated member and said slot and perforations being unaligned to deflect and lengthen the path of the fluid flow from said slot through said perforations; and means for applying an electric field across said perforated member and said diaphragm for producing an output signal representative of the variation in capacitance induced by the variation of the space between said perforated member and said diaphragm in response to an incident acoustic signal.

Claim 13

An acoustic transducer comprising: a perforated member; a movable diaphragm spaced from said perforated member; spring means interconnecting said diaphragm and said perforated member for movably supporting said diaphragm relative to said perforated member; a pressure equalization slot for controlling the flow of fluid through said diaphragm; said slot equalizing the pressure on opposite sides of the diaphragm for defining the low frequency response; a substantial portion of said slot being covered by said perforated member and said slot and perforations being unaligned to deflect and lengthen the path of the fluid flow from said slot through said perforations; and means for applying an electric field across said perforated member and said diaphragm for producing an output signal representative of the variation in capacitance induced by the variation of the space between said perforated member and said diaphragm in response to an incident acoustic signal.

Claim 14

The acoustic transducer of claim 11 in which said slot has a width of between 0.1 and 10μ.

Claim 15

The acoustic transducer of claim 11 in which said slot is disposed generally at the perimeter of said diaphragm.

Claim 16

The acoustic transducer of claim 13 in which said slot is approximately the length of the perimeter of said diaphragm.

Claim 17

The acoustic transducer of claim 11 in which said slot includes a plurality of sections.

Claim 18

The acoustic transducer of claim 11 in which said diaphragm is formed integrally with an insulator layer and said slot is formed at least partially between said conductive diaphragm and said insulator layer.

Claim 19

The acoustic transducer of claim 11 in which said slot is formed at least partially between portions of said conductive diaphragm.

Claim 20

The acoustic transducer of claim 11 in which said diaphragm, slot and spring means are made on a silicon wafer using micromachining photolithographic techniques.

Claim 21

The acoustic transducer of claim 11 in which said diaphragm and perforated member are made from a material from the group consisting of gold, nickel, iron, copper, silicon, polycrystalline silicon, silicon dioxide, silicon nitride, silicon carbide, titanium, chromium, platinum, palladium, aluminum and their alloys.

Claim 22

The acoustic transducer of claim 11 further including a filter spaced from said diaphragm for protecting said diaphragm from contaminants in the fluid.