## 5aAO5. Nonlinear acoustic interactions in liquids with bubbles and their applications for bubble measurements at sea.

### Session: Friday Morning, December 6

### Time: 9:20

**Author: Alexander M. Sutin**

**Location: Inst. of Appl. Phys., Russ. Acad. Sci., 46 Ulyanov str., Nizhny Novgorod, 603600, Russia**

**Author: Lev A. Ostrovsky**

**Location: Inst. of Appl. Phys.**

**Abstract:**

It is known that, in comparison with homogeneous media (e.g., water, air),
acoustical nonlinearity of a liquid with a small concentration of bubbles can be
anomalously high. The influence of bubbles upon nonlinear properties of the
medium is often much more significant than the simultaneous change of linear
characteristics, such as sound speed. This paper presents a brief review of our
investigations of nonlinear acoustic phenomena in bubble clouds, and some
results concerning nonlinear acoustic methods of measurements of bubble radii
and their distribution in water. (1) The theory of the bubble medium is based on
summation of the fields scattered by separate bubbles. The scattered field
consists of coherent and noncoherent parts, and the latter can be treated as a
nonlinear reverberation signal which takes place at frequencies different from
those of the incident acoustic wave: second harmonics in the case of a harmonic
primary radiator, and sum- and difference-frequency signals for a bifrequency
radiator. The formulas relating these signals to the bubble distribution in the
layer have been obtained. (2) To observe nonlinear acoustic effects in a
subsurface bubble layer and in sea sediments, two echosounders working at
different frequencies were used. The sum- and difference-frequency components
were observed in the signals scattered from sediments with bubbles and from the
subsurface bubble layer. The theory of such nonlinear scattering is in good
agreement with experimental data.

ASA 132nd meeting - Hawaii, December 1996