A system for measuring the transverse wave velocity and attenuation coefficients of underwater acoustic materials in parametric source method

A measurement system was provided for measuring an average transverse wave velocity and attenuation coefficients of underwater acoustic materials in the frequency range 10-100 kHz, with the characteristics of small size and narrow wave beam in the low frequency range. In the facility, a truncated parametric source was used as a testing sound source, together with a precision coordinate system. Based on theoretical modification and experiments for the plane wave model of sound pressure transmission coefficients of panels, the frequency and angle spectra of transmission coefficients (insertion loss) of panels were measured at first, then the average transverse wave velocity and attenuation coefficients were estimated using a curve-fitting means, an anechoic water tank, with a size 2 m×1 m×1.5 m, was used to measure some typed samples (500 mm×600 mm in size). The results showed that sound properties of underwater acoustic material samples were quite different at different incident angles of sound wave, and couldn't be replaced by the properties at an angle of vertical incidence. The transverse wave velocity and attenuation coefficients were important parameters for assessing sound properties of underwater materials, especially at an angle of oblique incidence. For investigations of material structures or complex parts, they were necessary and must be considered. The experiments had verified the measurement method and feasibility of the system. And it also showed that measurements in wider frequency band should be carried out to satisfy the actual need for the underwater acoustic engineering, so the measurement method should explored so that the facility can be used in the lower or higher frequency range.