A numerical study of the effects on acoustic propagation caused by dissipation in the atmosphere

By using a finite-difference time-domain method combining the dispersion relation preserving scheme in space and a Runge-Kutta scheme in time, the effect of dissipation on acoustic propagation is studied. It is shown that both trajectory and transmission loss of the wave packet are changed by the inhomogeneity of dissipation. Due to the inhomogeneous dissipation, the upper and lower part of the wave packet is attenuated at different levels, so that the energy center of the packet is shifted to the area where the dissipation is weaker, and the wave trajectory is refracted. As for the transmission loss, compared to the zero absorption case, the geometric spreading loss is reduced, and the atmospheric absorption is smaller than the constant absorption case. The dissipation makes acoustic propagation become dispersive because the attenuation coefficient is proportional to the square of frequency. The deflection of acoustic waves caused by the inhomogeneous dissipation is enhanced with increasing frequency.