Electro-acoustic transducer

Claim 2

An electro-acoustic transducer for providing electrical signals corresponding to sounds in a vibratory surface of a musical instrument, comprising (a) a relatively flexible body of plastic material; (b) a relatively rigid support member of plastic material for attachment to a musical instrument on a surface thereof which vibrates in accordance with sound produced by playing of the instrument; and (c) a capacitor microphone arrangement sandwiched between said support member and said body, said capacitor microphone arrangement comprising (i) a first electrode comprising an elongate foil of electrically conductive material; (ii) a second electrode comprising an elongate flat sheath of electrically conductive foil within which said first electrode is received; and (iii) a dielectric between said electrodes and electrically insulating said electrodes from one another.

Claim 3

An electro-acoustic transducer in accordance with claim 1, wherein said support member comprises a box open on one side and having an elongate base, and said microphone arrangement includes a double-sided self-adhesive tape which attaches said second electrode to said base, and said relatively flexible plastic material comprises a cold curing polyurethane compound substantially filling said box.

Claim 4

An electro-acoustic transducer in accordance with claim 2, wherein said box is made of high impact molded polystyrene.

Claim 5

An electro-acoustic transducer in accordance with claim 3, wherein the open side of the box is closed by a lid of plastic material attached to said cold curing compound by a double-sided self-adhesive tape.

Claim 6

An electro-acoustic transducer in accordance with claim 1, including a double-sided self-adhesive tape attached to said base of said box exteriorly thereof for attaching said box to a musical instrument.

Claim 7

An electro-acoustic transducer in accordance with claim 1, including a jack socket mounted on said box and having contacts electrically connected to said electrodes.

Claim 8

An electro-acoustic transducer in accordance with claim 1, wherein said support member comprises an elongate box having a lid, said microphone arrangement being mounted on said lid interiorly of said box, and said relatively flexible body of material comprises a strip of self adhesive plastic material overlying said microphone arrangement, and including a relatively rigid block of plastic material overlying and adhering to said strip.

Claim 9

An electro-acoustic transducer in accordance with claim 7, including a layer of double-sided self-adhesive tape attaching said microphone arrangement to said lid.

Claim 10

An electro-acoustic transducer in accordance with claim 7, wherein said lid comprises a polystyrene sheet, said strip comprises a cellular self-adhesive material, and said block is made of perspex.

Claim 11

An electro-acoustic transducer in accordance with claim 7, wherein said box includes a peripheral flange attached to the periphery of said lid.

Claim 12

An electro-acoustic transducer in accordance with claim 1, wherein said dielectric comprises a self adhesive tape attached to said first electrode.

Claim 13

An electro-acoustic transducer in accordance with claim 1, including a sensing circuit connected to said electrodes, said circuit including means for applying a substantially constant potential difference to said electrodes, and means for amplifying oscillatory voltages established between said electrodes.

Claim 14

The combination of a musical instrument, an electro-acoustic transducer for providing electrical signals corresponding to sounds in a vibratory surface of said instrument, said transducer being attached to said instrument on a surface thereof which vibrates in accordance with sound produced by playing of the instrument, said transducer comprising (a) a capacitor microphone arrangment comprising (i) a first electrode comprising an elongate foil of electrically conductive material; (ii) a second electrode comprising an elongate foil of electrically conductive material overlying said first electrode; and (iii) a dielectric between said electrodes and electrically insulating them from one another; (b) a housing of plastic material in which said microphone arrangement is received, said housing being mounted in intimate contact with said surface of said instrument, and adapted to transmit vibrations thereof to said capacitor microphone arrangement so as to produce relative movement of said electrodes in accordance with said vibrations; and (c) a sensing circuit connected to said electrodes, said circuit comprising means for applying a substantially constant potential difference to said electrodes, and means for amplifying oscillatory voltages established between said electrodes by said vibrations.

Claim 15

The combination of a musical instrument, an electro-acoustic transducer for providing electrical signals corresponding to sounds in a vibratory surface of said instrument, said transducer being attached to said instrument on a surface thereof which vibrates in accordance with sound produced by playing of the instrument, said transducer comprising (a) a capacitor microphone arrangment comprising (i) a first electrode comprising an elongate foil of electrically conductive material; (ii) a second electrode comprising an elongate foil of electrically conductive material overlying said first electrode; and (iii) a dielectric between said electrodes and electrically insulating them from one another; (b) a housing of plastic material in which said microphone arrangement is received, said housing being mounted in intimate contact with said surface of said instrument, and adapted to transmit vibrations thereof to said capacitor microphone arrangement so as to produce relative movement of said electrodes in accordance with said vibrations; and (c) a sensing circuit connected to said electrodes, said circuit comprising means for applying a substantially constant potential difference to said electrodes, and means for amplifying oscillatory voltages established between said electrodes by said vibrations.

Claim 16

The combination according to claim 13, wherein said housing comprises an elongate box having a lid, the capacitor microphone arrangement being received within and in intimate contact with a surface of said box, said box being substantially filled with a plastic material which is relatively flexible compared with the material from which the box is made.

Claim 17

The combination according to claim 13, wherein said second electrode comprises a sheath of said foil within which said first electrode is received.

Claim 18

The combination according to claim 13, wherein said housing includes an elongate box having a lid, said capacitor microphone arrangement being mounted on said lid, and including a layer of self adhesive material more flexible than said lid and overlying said capacitor microphone arrangement, and a block of rigid plastic material overlying said self-adhesive material.

Claim 19

The combination according to claim 13, wherein said sensing circuit includes a battery for applying said constant potential difference to said electrodes, an operational amplifier powered by said battery and arranged to amplify the oscillatory voltages established between said electrodes.

Claim 20

The combination according to claim 17, wherein said sensing circuit includes an input for receiving a source of direct current external to said circuit, and switching means arranged to select electric power for said circuit either from said external source or from said battery.

Claim 21

The combination according to claim 18, including a transformer having a primary winding connected to receive amplified signals from said amplifier, and a secondary winding connected to an output of the device.

Claim 22

The combination according to claim 18, including testing means for providing a visual indication that said constant potential difference has been applied to said electrodes.