...which may be classified as inhomogeneities of the liquid and at which the sound wave can lose energy (e.g. suspensions or air bubbles).
Classical attenuation is therefore the additive sum of the absorption mechanisms discussed above:
The classical attenuation coefficient can thus be written in closed form as:
Equation (3.20) clearly shows the frequency dependence of classical attenuation. Another useful representation, commonly employed in ultrasonic spectroscopy, is the attenuation over one wavelength λ:
Both representations contain a term involving numerous material parameters. Because this prefactor depends on the medium, it plays a special role in ultrasonic spectroscopy and is therefore assigned its own designation: the B value.2 In ultrasonic spectroscopy, B · f denotes the component of the spectrum extrapolated towards high frequencies, which in some cases may exceed the classical contribution. The following relationships apply:
3.1.1.2 Excess Attenuation
As already mentioned at the beginning of this chapter, one of the principal aims of ultrasonic spectroscopy is to infer physical processes and the causes of changes in material parameters from the attenuation properties of a solution. Owing to the complexity and diversity ...
Original typography of equations preserved. .