The acoustic domains in CdS caused by the two‐step pulse are studied with Ef an ultrasonic injection method and Brillouin scattering measurement. When the first‐step field Ef is smaller than the synchronous field Ea i.e., Ef?Ea , the factor m of fm ( f; frequency) of the lattice attenuation (αl) increases with increasing Ef and we finally obtained m = 2 at Ef = Ea. This means that the deviation from f2.0 is caused not only by the nonlinear process but also by the shock excitation. On the other hand, when Ef≳Ea, the amplitude of the current waveform decreased drastically and the maximum intensity of the frequency spectra becomes weak and it’s frequency becomes higher. This means that the nonlinear process is suppressed.