Acoustic impedance matching system

Claim 2

A transducer assembly comprising: a transducer; and a stratified medium for communicating acoustic wave energy between said transducer and a gaseous environment; said stratified medium being propagative of waves and having a depth along a direction of wave propagation of at least onequarter of the mean wavelength of the wave in the stratified medium, said stratified medium being formed of layers each of which presents a predetermined characteristic impedance to acoustic waves, said layers being arranged serially between said transducer and said environment along the direction of wave propagation such that there is presented to the propagating wave a variation in impedance characterized by substantially similar impedance ratios from the transducer through the successive layers to the gaseous environment; one of said layers being formed of acoustically transmissive foamable materials drawn from the class consisting of polystyrene foam, polypropylene foam, polyvinylchloride foam, and urethane foam, and means for improving the transmissivity of said acoustic wave energy between said stratified medium and said gaseous environment, said improving means being film structured and bonded to said stratified medium at an interface of said stratified medium with said gaseous environment.

Claim 3

A transducer assembly comprising: a transducer; and a stratified medium for communicating acoustic wave energy between said transducer and a gaseous environment; said stratified medium being propagative of waves and having a depth along a direction of wave propagation of at least one-quarter of the mean wavelength of the wave in the stratified medium, said stratified medium being formed of layers each of which presents a predetermined characteristic impedance to acoustic waves, said layers being arranged serially between said transducer and said environment along the direction of wave propagation such that there is presented to the propagating wave a variation in impedance characterized by substantially similar impedance ratios from the transducer through the successive layers to the gaseous environment; at least one of said layers being a composite material comprising regions of solid matter and regions of fluid matter, said one layer having a composite acoustic impedance resulting from the coaction of the regions of solid matter and the regions of fluid matter, the dimensions of said fluid region along the direction of wave propagation being less than one-tenth of the mean wavelength of the wave propagating within said layer, the layer of said stratified medium adjacent said transducer being solid elastomer and the layer of said stratified medium adjacent the environment being foam structured; two of said layers each having a depth of one-quarter of the mean wavelength of sound propagating through that layer, said layer adjacent said transducer being formed of polyurethane, and the second layer being formed of acoustically transmissive foamable materials drawn from the class consisting of polystyrene foam, polypropylene foam, polyvinylchloride foam, and urethene foam; said stratified medium further including a third layer, said second layer being composed of urethene foam, and said third layer being composed of polytetrafluoroethylene and having a depth of less than one-tenth the mean wavelength of sound propagating through the layer.

Claim 4

A transducer assembly comprising: a transducer; and a stratified medium for communicating acoustic wave energy between said transducer and a gaseous environment; said stratified medium being propagative of waves and having a depth along a direction of wave propagation of at least one-quarter of the mean wavelength of the wave in the stratified medium, said stratified medium being formed of layers each of which presents a predetermined characteristic impedance to acoustic waves, said layers being arranged serially between said transducer and said environment along the direction of wave propagation such that there is presented to the propagating wave a variation in impedance characterized by substantially similar impedance ratios from the transducer through the successive layers to the gaseous environment; at least one of said layers being a composite material comprising regions of solid matter and regions of fluid matter, said one layer having a composite acoustic impedance resulting from the coaction of the regions of solid matter and the regions of fluid matter, the dimensions of said fluid region along the direction of wave propagation being less than one-tenth of the mean wavelength of the wave propagating within said layer, the layer of said stratified medium adjacent said transducer being solid elastomer and the layer of said stratified medium adjacent the environment being foam structured; two of said layers each having a depth of one-quarter of the mean wavelength of sound propagating through that layer, said layer adjacent said transducer being formed of polyurethane, and the second layer being formed of acoustically transmissive foamable materials drawn from the class consisting of polystyrene foam, polypropylene foam, polyvinylchloride foam, and urethene foam; said stratified medium further including a third layer, said second layer being composed of urethene foam, and said third layer being composed of polytetrafluoroethylene and having a depth of less than one-tenth the mean wavelength of sound propagating through the layer.

Claim 5

The transducer assembly of claim 2 wherein said transducer has a surface which vibrates in response to electrical stimulation.

Claim 6

The transducer assembly of claim 3 wherein said transducer assembly further includes electrical connection means and a transformer, said transformer being in circuit between said transducer and said electrical connection means whereby electrical signals are communicated to the transducer.

Claim 7

The transducer assembly of claim 4 wherein said transducer assembly further includes a structure for supporting said stratified medium and said transformer in spaced relation to said transducer.

Claim 8

A first medium for communicating acoustic wave energy between a gaseous environment and a second medium having an acoustic impedance higher than that of the gaseous environment, said first medium being formed of layers arranged serially between said second medium and said gaseous environment; a first one of said layers comprising a solid polyurethane elastomer having a density of approximately 71.8 pounds per cubic foot and a Shore A durometer in the range 75-95; and a second one of said layers comprising a polystyrene foam having a closed cell composition and a density of 2 pounds per cubic foot.

Claim 9

A first medium for communicating acoustic wave energy between a gaseous environment and a second medium having an acoustic impedance higher than that of the gaseous environment, said first medium being formed of layers arranged serially between said second medium and said gaseous environment; a first one of said layers comprising a solid polyurethane elastomer having a density of approximately 71.8 pounds per cubic foot and a Shore A durometer in the range 75-95; and a second one of said layers comprising a polystyrene foam having a closed cell composition and a density of 2 pounds per cubic foot.

Claim 10

The medium according to claim 6 wherein the cells in the polystyrene foam have dimensions which are less than one-tenth the sound wavelength in the polystyrene foam.

Claim 11

The medium according to claim 7 wherein the depth of said first layer and of said second layer is each an odd integral number of one-quarter wavelengths of the sound wavelengths within the respective layers.

Claim 12

A first medium for communicating acoustic wave energy between a gaseous environment and a second medium having an acoustic impedance higher than that of the gaseous environment, said first medium being formed of layers arranged serially between said second medium and said gaseous environment; a first one of said layers comprising a solid polyurethane elastomer having a density of approximately 71.8 pounds per cubic foot and a Shore A durometer in the range 75-95; and a second one of said layers comprising a foam material drawn from the class consisting of a polypropylene foam with rubber particles suspended therein, polystyrene foam, polyvinylchloride foam, and urethane foam.

Claim 13

A first medium for communicating acoustic wave energy between a gaseous environment and a second medium having an acoustic impedance higher than that of the gaseous environment, said first medium being formed of layers arranged serially between said second medium and said gaseous environment; a first one of said layers comprising a solid polyurethane elastomer having a density of approximately 71.8 pounds per cubic foot and a Shore A durometer in the range 75-95; and a second one of said layers comprising a foam material drawn from the class consisting of a polypropylene foam with rubber particles suspended therein, polystyrene foam, polyvinylchloride foam, and urethane foam.

Claim 14

The medium according to claim 9 in which said second layer comprises urethane foam and a third one of said layers comprises polytetrafluorethylene.

Claim 15

A first medium for communicating acoustic wave energy between a gaseous environment and a second medium having an acoustic impedance higher than that of the gaseous environment, said first medium comprising: a plurality of layers arranged serially between said second medium and said gaseous environment; said first medium being propagative of waves and having a depth along a direction of wave propagaTion of at least one-quarter of the mean wavelength of the wave in said first medium; one of said layers being formed of acoustically transmissive foamable materials drawn from the class consisting of polystyrene foam, polypropylene foam, polyvinylchloride foam, and urethane foam; and means for improving the transmissivity of said acoustic wave energy between said first medium and said gaseous environment, said improving means being film structured and bonded to said first medium at an interface of said first medium with said gaseous environment.

Claim 16

A first medium for communicating acoustic wave energy between a gaseous environment and a second medium having an acoustic impedance higher than that of the gaseous environment, said first medium comprising: a plurality of layers arranged serially between said second medium and said gaseous environment; said first medium being propagative of waves and having a depth along a direction of wave propagaTion of at least one-quarter of the mean wavelength of the wave in said first medium; one of said layers being formed of acoustically transmissive foamable materials drawn from the class consisting of polystyrene foam, polypropylene foam, polyvinylchloride foam, and urethane foam; and means for improving the transmissivity of said acoustic wave energy between said first medium and said gaseous environment, said improving means being film structured and bonded to said first medium at an interface of said first medium with said gaseous environment.

Claim 17

The first medium according to claim 11 wherein one of said layers is a composite material comprising regions of solid matter and regions of fluid matter, said regions of fluid matter being prestressed cells of fluid.