Patent ID: 6831876
Filing Date: 2004-12-14
Classification: G10K,Y10S

Abstract:
An improved acoustic window for an acoustic waveform passage having a generally uniform transmission loss at an angle of incidence of between âˆ’40Â° and +40Â° comprising a laminate composition formed from at least one core layer and at least two septa, said core layer comprising a material having a generally low-acoustic-impedance, a static shear modulus between about 1.0 psi (0.07 MPa) and about 15,000 psi (103 MPa), an average transverse (or through-thickness) sound velocity for the acoustic waveform of between about 700 and about 2200 meters per second, a transverse acoustic impedance of less than or equal to 4Ã—106 kilograms per square meter-second, and a shear loss factor of greater than 0.02,each of said septa being composed of at least one ply of a material having a transverse acoustic impedance of less than 60Ã—106 kg/m2-sec, a thickness of less than 0.10 &lgr;M wherein &lgr;m is the wavelength of an acoustic wave in the material, a tensile modulus of more than 0.5Ã—106 psi, and being bonded to said core to form a sandwich with said core layer, and the acoustic waveform having a &lgr; of at least 0.001 meter and less than 3 meters.