Acoustic Performance Measurement Of Marine Passive Materials Based On Time Reversal Technique

Acoustic material components are widely used, and they are vital underwater parts in acoustic engineering. Different application backgrounds have different requirements on acoustic materials performance. With the development of material science, viscoelastic polymer materials and other high performance absorption new materials are applied widely in the absorption and noise reduction underwater acoustic engineering field. Therefore, researching the acoustic materials performance is the urgent problem.Acoustic passive materials performance parameters include insertion loss (transmission coefficient), echo reduction (reflection coefficient), sound absorption coefficient and others. At present acoustic passive materials'performance measurement has made important progress in high frequency band, but with the development of sonar technology, the acoustic performance measurement in low frequency band is needed.Time reversal focusing technique takes full advantage of multipath characteristics of sound propagation in the waveguide environment, summing all paths in the same phase. The temporal compression of the time-reversal focusing increases the signal strength, and improves signal reverberation ratio. The spatial compression of the time-reversal focusing makes the main lobe narrower than the plane wave beam-forming, reducing the influence of diffraction. This article researches the time reversal focus measurement method through the theory simulation analysis and field test.In order to have the best result of time reversal in a closed cylindrical vessel environment, the best receive array and transmitting array combination is designed after the analysis of the resolution of the main lobe.In order to make the measurement results are consistent with in free field conditions, the paper put forward the correction method of measuring parameters through the theoretical analysis. The passive materials are tested in the waveguide pool under normal pressure and the pressure vessel environment under normal,2MPa, 3MPa and 4MPa pressure. The experiment results are consistent with the theoretical value. This result proves that time reversal technology is another way to test the passive materials' performance parameters.