Finite elastic coupling effects in critical sound propagation in dilute Ising systems

The nonasymptotic critical properties of sound propagation induced by finite spin-strain coupling are studied in dilute Ising model aboveT _c by means of renormalization group methods and expansion. It is shown that effective hydrodynamic sound attenuation exponent is lower in compressible systems than in the almost rigid ones. Scaling functions for sound attenuation and dispersion are obtained in the crossover region to the first order.