Method and apparatus for a phased array transducer

Phased array transducer apparatus for receiving or transmitting an acoustic wave in a transmission external medium comprising:

• electroacoustic transducer means for converting between acoustic and electrical signals;
• said transducer means having first and second vibratile surfaces;
• tube means having first and second ends, an end to end axis, and an acoustic interior passage;
• means for supporting said transducer means along said tube means so that said first vibratile surface is acoustically coupled to the transmission external medium and said second vibratile surface is acoustically coupled to said interior passage;
• port means comprising at least a pair of first and second ports, each port being formed in said tube means for conducting acoustic waves between said interior passage and the transmission external medium;
• said tube means being of a material having a different acoustic characteristic impedance to acoustic waves than said liquid transmission external medium to provide an acoustic transmission path boundary for acoustic waves traveling interiorly of said tube means between said transducer means and said port means;
• said port in said port means having an acoustic characteristic impedance so that there is provided substantially unattenuated transmission of acoustic waves through said ports;
• said first port in said pair of ports being spaced a predetermined distance in a first axial direction from said transducer means and said second port in said pair of ports being spaced a predetermined distance in a second axial direction different from said first direction, so that within a frequency band of transducer operation a reinforcing combination between the acoustic waves impinging upon or radiating from said first and second vibratile surfaces provides maximum radiation of acoustic waves in the transmission external medium or maximum response to acoustic waves in the liquid transmission external medium in a direction broadside said axis.

Transducer array apparatus for receiving or transmitting in a frequency band of operation an acoustic wave having a predetermined frequency and corresponding wavelength in a transmission external medium comprising:

• electroacoustic transducer means for converting between acoustic energy and electrical energy for transmitting or receiving acoustic waves;
• said transducer means having first and second vibratile surfaces;
• tube means having first and second ends, an end to end axis, and an acoustic interior passage;
• means for supporting said transducer means at a predetermined axial location along said tube means so that said first vibratile surface is acoustically coupled to the transmission external medium and said second vibratile surface is acoustically coupled to said interior passage;
• port means comprising at least a pair of first and second ports, each port being formed in said tube means for conducting acoustic waves between said interior passage and said transmission external medium;
• said tube means being of a material having a different acoustic characteristic impedance to acoustic waves than said liquid transmission external medium to provide an acoustic transmission path boundary for acoustic waves traveling interiorly of said tube means between said transducer means and said port means;
• said ports in said port means having an acoustic characteristic impedance so that there is provided substantially unattenuated transmission of acoustic waves through said ports;
• said first port in said pair of ports being spaced a first predetermined distance in a first axial direction from said transducer means and said second port in said pair of ports being spaced a predetermined distance from said transducer means, so that within the frequency band of transducer apparatus operation including said predetermined frequency a reinforcing combination between the acoustic waves impinging upon or radiating from said first and second vibratile surfaces is provided whereby there is a maximum radiation of acoustic waves or maximum response to acoustic waves in the liquid transmission external medium in a direction broadside said axis.

A method of providing an acoustic array for receiving and/or transmitting acoustic waves having respective predetermined wavelengths in a liquid external medium comprising the steps of:

• a first step of converting between electrical signals and first and second acoustic waves out of phase with one another at an active conversion area along a tube having an end to end axis so that said first wave is in acoustic communication with the external medium and said second wave is in acoustic communication with an acoustic wave conducting internal medium within the tube;
• a second step of providing an acoustic wave travel path in the internal medium of the tube between said conversion area and at least one acoustic conducting area along the tube;
• said conducting area for conducting acoustic waves between the internal medium and the external medium and said conducting area being axially spaced apart from said conversion area;
• the tube being of a material having a different acoustic characteristic impedance to acoustic waves than the external medium to provide an acoustic transmission path boundary for acoustic waves traveling interiorly of the tube between said conversion area and said conducting area;
• a third step of providing said acoustic wave travel path between said conversion area and said conducting area with an effective acoustic length so that said first wave at said conversion area and said second wave at said conducting area are substantially in phase and said first and second waves respectively at said conducting area are substantially out of phase.