## 4aPA8. Nonlinear effects on acoustic field measurement in biomedical frequency range.

### Session: Thursday Morning, May 16

### Time: 10:00

**Author: S. G. Ye**

**Author: X. F. Gong**

**Author: X. Z. Liu**

**Location: Inst. of Acoust. and Lab. of Modern Acoust., Nanjing Univ., Nanjing 210093, People's Republic of China**

**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.]

from ASA 131st Meeting, Indianapolis, May 1996