Pressure compensating coaxial line hydrophone and method

Abstract

The utility of a coaxial electret cable transducer as a hydrophone at shallow depths (low hydrostatic pressure) is extended for operation at substantially greater depths (high hydrostatic pressure) by the combination of the electret with a polymer material having piezoelectric properties, i.e., a piezoid. The electret and piezoid are separate flexible materials radially stacked within the cable or alternatively and preferably constitute a single material formed to have both electret and piezoelectric properties. One substance useful as the piezoid or as the electret-piezoid combination is polyvinylidene fluoride (PVF.sub.2). The invention also comprehends the method of measuring underwater soundings at either low or high hydrostatic pressures with the aforementioned coaxial cable as an electrostatic transducer by measuring electrical signals generated across the cable conductors when the ambient pressure is low and as a piezoelectric transducer across the conductors when such pressure is high.

Dependencies are inferred from the claim text.