The nonlinear propagation of acoustic waves in a viscoelastic medium containing cylindrical micropores

Based on an equivalent medium approach, this paper presents amodel describing the nonlinear propagation of acoustic waves ina viscoelastic medium containing cylindrical micropores. Theinfluences of pores' nonlinear oscillations on soundattenuation, sound dispersion and an equivalent acoustic nonlinearityparameter are discussed. The calculated results show that theattenuation increases with an increasing volume fraction ofmicropores. The peak of sound velocity and attenuation occurs at theresonant frequency of the micropores while the peak of theequivalent acoustic nonlinearity parameter occurs at the half of theresonant frequency of the micropores. Furthermore, multiplescattering has been taken into account, which leads to amodification to the effective wave number in the equivalent mediumapproach. We find that these linear and nonlinear acousticparameters need to be corrected when the volume fraction ofmicropores is larger than 0.1%.