Relaxation mechanisms features of ultrasonic absorption in soft tissues
Abstract
In the present paper it has been shown that universal linear dependence of absorption coefficient of ultrasound practically in all soft tissues can be explained only in case of consideration the multiplicity of relaxation mechanisms. Besides totality of these mechanisms is characterized by wide range of relaxation time on the molecular and cellular level. At that the weighting function with inverse proportion time dependence leads to experimentally observed in soft tissues frequency dependence of attenuation coefficient which is closed to linear. In case of wide range of frequency the similar dependence can be typical even for biological objects with relatively small number of degrees of freedom. In the general case of assumed contribution of different relaxation mechanisms various functional frequency dependences for velocity of sound and attenuation coefficient which can be observed.
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