Standard Calibration Hydrophone

Abstract

A new calibration standard hydrophone for use in the frequency range 5 cps to 150 kc is described. The active element is a lithium sulfate crystal on a tungsten backing plate. The free-field voltage sensitivity (end-of-cable) is −90±3 db re 1 v per μbar throughout most of the frequency range. The sensitivity is little affected by temperature changes in the range 1° to 25°C, and is not affected by hydrostatic pressure changes in the range 0 to 1000 psig. Directivity patterns are very nearly those to be expected from a 1-in. piston.

Bilateral CMUT Cells and Arrays: Equivalent Circuits, Diffraction Constants, and Substrate Impedance

“…With 135 V bias, V dc /V r = 0.784, and CBC, (13) yields X P +X P = 0.1707t ge for this bias level. The static transduction force, F R , is found as 5.12 × 10 −4 Nt under same conditions, using (17). The center deflections of the front and back plates are determined as 90 and 38 nm, respectively, using (7) and (8), which matches to the FEA results reported in [8,Fig.…”

“…Transducers with uniform surface velocity are extensively studied [10], [17]- [21]. It is known that the diffraction constant, radiation resistance, and the directivity factor of such transducers are interrelated [10].…”