Device for Measuring the Properties of Acoustic Materials at Low Frequency UnderPressure

摘要

Development of materials for underwater acoustic applications requiresmeasurement facilities for characterizing acoustic performance. Existing facilities are generally suitable for making measurements in the frequency range above 1 kHz. These include the pulse tubes located at NSWC/Annapolis and the anechoic tank located at NRL/Orlando. Under the Attenuation Materials Program of the Office of Naval Research, capabilities for characterizing acoustical materials in the frequency range below 1 kHz are being developed and improved. As part of this effort, Cambridge Acoustical Associates has designed and developed a laboratory testing device for evaluating acoustical materials below 1 kHz at hydrostatic pressures up to 500 psig. Several unique testing capabilities are designed into this device. Sufficient measurements are made on inertially-backed samples to obtain a two-port impedance representation of the material. A water layer coupling the excitation piston and the face of the material sample permits realistic loading of spatially inhomogeneous materials under hydrostatic pressure. The design of the device is documented in Ref. 1. In this report the performance of the device is evaluated.