Title: The parametric source method for measuring characteristics of underwater acoustic materials in a pressure vessel

Author(s): LI Shui; YI Yan; ZHANG Jun;

Affiliation(s): Hangzhou Applied Acoustics Research Institute;

Abstract: A truncated broadband parametric array with a primary frequency of 500 kHz and difference frequency range of 1 kHz to 30 kHz was designed as a sound source of the underwater acoustic material measurement system. By analyzing the theoretical calculation and actual measurement results in array directivity of the truncated broadband parametric source at typical frequencies, we observed that the curves of the two results were basically consistent, which proved that the calculation model was correct. Application of bell-shaped short-duration pulse to achieve broadband measurement for characteristics of underwater acoustic materials was beneficial to reduce the effects of diffraction from the panel edges. The measurement system was established for measuring the sound pressure reflection coefficients, sound pressure transmission coefficients and absorption coefficients of the large panel sample in the pressure vessel. The size of this tank is ？4 m×12 m, the maximum hydrostatic pressure is 4.5 MPa, and the corresponding measuring frequency range is from 1 kHz to 30 kHz. The measured curves had a good agreement with theoretical curves, which verified that the parametric source measurement method was feasible. Then, the sound absorption properties of the rubber plate sample were measured under different hydrostatic pressures. The studying results could show that the parametric source measurement method had the potential application in the limited space water, such as the pressure vessel.