On the stability of acoustic waves propagating in a nonstationary moving medium

We analyze the stability of acoustic waves in a medium moving with a time-variable velocity. An instability criterion for these waves is obtained and analyzed for the weak modulation of medium velocity. The harmonics that emerge during the propagation under parametric resonance are shown to have an additional frequency shift.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 9, pp. 1087–1090, September, 1996.This work was supported by the Russian Foundation for Fundamental Research under Projects 95-02-05001 (G. I. Grigor'ev and V. V. Tamoikin) and 96-05-64277 (O. N. Savina).