The Aging of Cork-Rubber Decoupling Materials

摘要

Pressure-release materials are used to insulate come components of sonar transducers. By acoustically shielding some areas of the transducer, the directivity and sensitivity can be greatly altered. Pressure-release materials/insulate because of their large differences in acoustic impedance from that of the other components and fluids used in transducers. One serious problem is that these pressure-release materials absorb the transducer fill fluids. This increase the acoustic impedance and therefore reduces the effectiveness of the acoustic insulation. The absorption mechanism is investigated by microscopic analysis, gravimetric analysis, and microtome sectioning. An explanation of the fluid permeation mechanism is offered along with the time-temperature dependence. Resulting changes in the acoustic properties with fluid absorption are studied using an acoustic impedance tube and G19 hydrophone calibrator. An equation is formulated to predict the changes in sensitivity of a simple hydrophone resulting from aging of its pressure-release material. (Author)