THE EFFECT OF RECEIVER SIZE ON NONLINEAR PRESSURE FIELD-MEASUREMENTS

The nonlinear pressure field generated by an ultrasonic source many wa velengths in diameter is studied experimentally and theoretically usin g two different size receivers. One receiver is sufficiently small to be considered infinitesimal at most positions in the pressure field wh ile the other receiver has a diameter equal to that of the source. The oretical predictions are made using a numerical solution of the KZK eq uation and these show that the large receiver virtually eliminates the pressure field fluctuations normally observed with a small receiver a long and across the acoustic axis. To a large extent the axial field o bserved with the large receiver resembles a plane-wave field. The pred ictions are compared with experimental measurements obtained with a pl ane piston transducer (38-mm-diam, 2,25-MHz center frequency) as a sou rce, and hydrophones 1 mm and 38 mm in diameter. Good agreement is see n between experiment and theory. (C) 1996 Acoustical Society of Americ a.