A theory of ultrasonic absorption in liquids

A theory has been developed for the complex and frequency-dependent compressibility of a liquid under the action of an ultrasonic wave in terms of the frequency of the wave (ω), a relaxation time which is a function of the physical properties of the medium and the low frequency and high frequency compressibilities. The locus of the compressibility as ω changes from 0 to ∞ is a semicircle. Suitable expressions are obtained for the relaxation time (τ) and the maximum absorption per wavelength, (αλ)ωc, in terms of the real and imaginary components of the compressibility, which are also connected with absorption and dispersion of ultrasonic waves in the liquid. Values of τ and (αλ)ωc are evaluated using available experimental data of ultrasonic absorption and dispersion. It is found that the agreement between the relaxation times calculated using the various formulae is fairly good. © 1974.