  A cosmological first-order phase transition gravitational wave could provide
a novel approach to studying the early Universe. In most cases, the acoustic
gravitational wave from the sound wave mechanism is dominant. Considering
different sound velocities in symmetric and broken phases, we study sound
velocity effects on the acoustic phase transition gravitational wave spectra in
the sound shell model. We demonstrate that different sound velocities could
obviously modify the peak frequency and peak amplitude of the gravitational
wave power spectra. Therefore, taking more realistic sound velocities might
provide more accurate predictions for various gravitational wave experiments.
