Abstract:
It was shown that ultrasound propagation in media is accompanied with nonlinear phenomena and the nonlinear effects on the measurement of acoustic field cannot be neglected. A needle hydrophone was used to receive the signal in the acoustic field for further analysis and the radiation force method was used to measure the total output power of the transmitter. The case of emitting power was constant, the nonlinear phenomena were accumulated due to the distance between the transmitter, and the hydrophone increased from a few centimeter to less than 20 cm. With increasing distance between the transmitter and the hydrophone, the ultrasound energy was gradually transferred from fundamental frequency f[inf 0] to high harmonics. Using the spectrum analyzer, the dependence of f[inf 0] and nf[inf 0] (n=2,3,...) on the distance increased was measured. When the distance between the transmitter and the hydrophone was fixed, the nonlinear phenomena became stronger as the emitting power increased. The acoustic intensity of f[inf 0] was no longer linearly increased with the increased emitting power acoustic intensity, and the acoustic intensity of f[inf 0] would tend toward a saturation value. [Work supported by NSFC.]