Broadband Test Method For Acoustic Properties Of Large Underwater Sample Materials

The research of underwater acoustic overlay materials has always been an important research direction of underwater vehicle acoustic stealth technology,because acoustic overlay materials are mostly non-uniform structures,it is difficult to simulate from theory,acoustic material performance testing is an important method for its application evaluation,which can provide a test basis for the design of acoustic overlays.With the deepening of acoustic material research,the performance of acoustic materials gradually develops to low frequency,and has a larger size in structural design,the traditional acoustic tube small-size sample test method can no longer meet the actual needs,and the acoustic performance test method of large-size sample has become an important direction for the development of acoustic performance testing technology.Aiming at the influence of wall reflection in limited space on the test,based on the traditional pulse method to measure the acoustic performance of acoustic materials,combined with the measurement theory of transfer function method in the sound tube,the long pulse transfer function method of material acoustic performance is established,and the influence of pulse width,time period selection and test signal-to-noise ratio on the test is theoretically analyzed,and the feasibility of the simulation analysis method is simulated.The acoustic performance test analysis of the pressure bucket using a uniform steel plate with a side length of 1.8m with a thickness of 10 mm was used: the deviation between the measured value of the reflection coefficient and the theoretical value in the pressure environment above 1KHz was less than 0.1,and the deviation between the test value of the sound insulation amount and the theoretical value was less than 1d B,which showed the reliability of the test method.Aiming at the influence of wall reflection in limited space on the test of long pulse transfer function method,broadband pulse emission technology and inverse filtering method are adopted,and the broadband narrow pulse transfer function method of material acoustic performance is established on the basis of long pulse transfer function method.The model test of uniform steel plate shows that the reflection coefficient deviation is less than 0.1 and the sound insulation measurement deviation is less than 2d B in the frequency band above 500 Hz,which verifies the reliability of the broadband measurement method.The test frequency band is wider than the traditional measurement method,and the test efficiency is higher.The broadband measurement method of acoustic performance of underwater large-sample acoustic materials established in this paper can provide a measurement method for the evaluation of acoustic performance of underwater large-scale samples.