Abstract:
The difference-frequency sound generation as a result of the interaction of two high-frequency harmonic waves in a bubble layer in water are investigated experimentally and theoretically. As it was shown before, the use of the layer resonance can increase the efficiency of the nonlinear transformation of the signal. Here the data of the experiment with a bubble layer of the thickness of about 10 cm in the anechoic tank are presented. One of the incident (primary) wave frequencies was 60 kHz while the another varied from 59 to 50 kHz, thus providing the low-frequency signal in the range of 1 to 10 kHz. Due to the first-mode layer resonance, this secondary signal had a pronounced maximum at the frequency of 2.2 kHz (while the primary wave was in resonance with the bubbles of the radius about 45 (mu)m, and no resonance in the layer was observed for it). The bubble volume ratio from these experiments was estimated to be about 1.4x10[sup -4]. A theory was also developed for this type of interaction which described well the experimental results. [Work was supported by the Russian Foundation of Fundamental Research Grant No. N0-93-05-8074 and by the Science Opportunity Program of the Office of Naval Research.]