The study of sound propagation in granular beds at frequencies exceeding a MHz has been a subject of study for many years. Much remains to be learnt about sound propagation at lower frequencies. We shall present our studies on the problem of impulse propagation and briefly comment on low frequency acoustic propagation in model granular beds using particle dynamical simulations. The following results will be briefly discussed. (i) Impulses propagating as solitary waves in 1-D granular chains with Hertz contacts in the absence of precompression. (ii) The effects of uniform precompression and gravitational loading on wave propagation. (iii) Impulse propagation in 3-D granular beds. The research presented shall highlight the intrinsically nonlinear nature of wave propagation in granular beds.