Abstract:
The wave energy localization in the process of sound propagation in the media with fractal structure leads to the frequency dependence of the nonlinear response. In the low-frequency range, a sound wave, propagated through the water-saturated granular matter, has a typical attenuation, related to the Biot theory. In the range of fractal structure, spatial scales oscillations occur as localized ones. This state of oscillations is known as fractons. The appropriate spectrum of oscillations is related to the fractal dimension of the studied media and falls drastically with the frequency. Experiments of finite-amplitude, wide frequency sound pulse propagation through the sample of cobalt--manganese crust deposits are analyzed with respect to appropriate computer-simulated models. Abnormally large sound attenuation at relatively small-amplitude signal propagation in the frequency range up 0.7 MHz, was shown, while at the large signal amplitude, the value of the signal attenuation falls and reaches the Biot frequency pattern. [Work supported by the Russian Basic Research Foundation, Grant No. 95-02-06353.]