| 摘要 |
PROBLEM TO BE SOLVED: To provide a simple and easy measuring method in the atmosphere of the sound velocity of underwater sound absorbing material. SOLUTION: Piezoelectric sheets 10, 20 are placed on both faces of the underwater sound absorbing material, and an impact wave is imparted onto the center of the upper face by drop of an impact ball 300. Signals of the piezoelectric sheets 10, 20 are stored by a waveform storage device 30. By using the ratio k of a ratio station 40, the time Ta when the signal of the piezoelectric sheet 10 becomes the value of kA to the peak value A of the piezoelectric sheet 10 is calculated by a constant ratio amplitude time calculator 50, and the time Tb when the signal of the piezoelectric sheet 20 becomes kB to the peak value B of the signal of the piezoelectric sheet 20 is calculated by a constant ratio amplitude time calculator 60. By using the ratio c set by a ratio station 80, the time To when the signal of the piezoelectric sheet 20 becomes cB to the peak value B is calculated by a constant ratio amplitude time calculator 70. The difference Tm between the times Ta, Tb is calculated by a time difference calculator 90 and the difference Tr between the times To, Tb is calculated by a time difference calculator 100. Then, the sound velocity V of the underwater sound absorbing material is calculated by the expression V=L/(Tm-P*Tr) by a sound velocity calculator 110 by using the ratio p set by a ratio station 120. COPYRIGHT: (C)2003,JPO
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