Analysis of the Acoustic Characteristics of Absorptive Material in Airborne and Underwater Field

Ruey-Chang Wei ； Shih-Ming Chiu ； Jyin-Wen Cheng

《機械技師學刊》 8卷3期 (2015/10) Pp. 12-21

https://doi.org/10.6208/JPME-2015-10-02

並列摘要

Noise control underwater was thoroughly investigated during World War II and since then, Germany has used air-rubber composite mats to disguise submarine acoustics from active sonar, for defense purposes. However, the mats original design exhibited inherent problems of degradation under hydrostatic pressure and extreme temperatures that have not yet been solved. In this study, we used five specimens of the acoustic materials which were mainly made of neoprene and sawdust mixtures to evaluate the acoustic characteristic in airborne and underwater fields. The mechanical and acoustic properties were measured for sample data through experimentation. All of the specimens very nearly matched the acoustic impedance of water. In order to obtain the characteristics of an acoustic evaluation underwater, a horizontal, high pressure water chamber was applied to the experiment. The chamber was a closed system, water-filled and pressurized for acoustic testing of underwater materials and devices. Echo Reduction (ER) and Insertion Loss (IL) were measured to evaluate acoustic absorption under various hydrostatic pressures for specimen data. The results of the experiments showed that, for all of the test specimens, there was a decrease in the level of ER due to hydrostatic pressure. And it also appeared that the higher the frequency, the heavier the echo reduction. The results showed agreement with acoustic material in airborne. Furthermore, the IL was measured under various hydrostatic pressures and the resulting measurements clearly showed that materials from specimens A_1 and A_2 are viable for underwater acoustic absorptive.

並列關鍵字

underwater acoustic ； absorptive material ； echo reduction ； insertion loss