ABSTRACT
Sound-pressure measurements are usually performed using calibrated hydrophones. For determining the total radiated power, a radiation force measurement is the most handy and exact method. Optical measurement procedures result in a high resolution in space and/or in time without disturbing the sound field, but they require rather sophisticated measurement devices. In making preparations for hydrophone measurements, one is confronted with the problem of finding an appropriate hydrophone which fulfills several fundamental specifications, i.e., it should be small in relation to the wavelength, adequately sensitive, broad banded, and temporally stable. In order to minimize the consequences of the spatial averaging effect, there are certain requirements to be fulfilled. Several standards addressing the measurement problem recommend values for the maximum effective hydrophone size to be used in a given ultrasonic field. Hydrophones with piezoceramic material are subject to additional disturbances due to the considerable cross-coupling which leads to the excitation of radial modes and their overtones.
