Forty years of nonlinear ultrasound.
Nonlinear ultrasound forms an integrated discipline of nonlinear acoustics founded in 1755. A short outline of the state-of-the-art in nonlinear ultrasound in 1960 forms the introduction to this paper. Some of the most important contributions to the development in the theoretical, analytical and numerical basis of nonlinear ultrasound and in experimental investigations of nonlinear ultrasonic processes published during the period of 1960 through 2000 are discussed and their successes and failures in practical exploitation are illuminated. A more detailed treatment is given of research achievements in nonlinearity of fluids, in focused ultrasonic field, in parametric acoustic arrays and in thermoacoustics. An attempt is made to point out some fields of research in nonlinear ultrasound where future efforts should be concentrated.