抄録
The nonlinearly distorted sound in a focused Gaussian beam with insertion of a liquid layer different from the surrounding medium (water) is examined by theory and experiment. Under the approximation that the radial distribution profiles of amplitude and phase of each harmonic component are independent of excitation level, the simplified equation for the Fourier coefficient describing the complex amplitude of harmonic component was numerically solved by the finite difference method. A circular concave piezoelectric transducer with a star-shaped electrode was employed for a focusing Gaussian source in the experiment. The sound waveforms at various points after the liquid layer were observed to obtain the distribution of amplitudes and phases for the harmonic components. The comparison of the theory and experiment led to the conclusion that, although a slight discrepancy appeared between them at large amplitude because of the restricted assumption of the present theory, they agreed well at moderate amplitude.
