Transducer transmitting sensitivity is normally measured under free-field c
onditions. In laboratory tanks, this is often achieved by using time gating
to isolate the direct signal from the reflected signals. However for high-
e, low-frequency projectors, the free-time availability in laboratory tanks
may be too short. A measurement technique has been developed to perform th
ese calibration measurements in the presence of a reverberant field. The me
asurements have been performed at ultrasonic frequencies so that the free-f
ield sensitivity can be determined in order to assess the accuracy of this
new technique. The technique involves extracting the direct held from the c
ombination of the direct and reverberant fields by plotting the variation o
f pressure squared against the reciprocal of separation squared. The gradie
nt of this graph is proportional to the acoustic power radiated into the ta
nk, and from this, the direct field pressure and projector sensitivity can
be calculated. This paper investigates this technique and looks at the infl
uences of tank size and construction, as well as the effect of averaging ov
er different bandwidths. (C) 2000 Elsevier Science B.V. All rights reserved
.