Optical wave microphone technology was originally developed in the field of plasma nuclear fusion. It was developed as a measurement method for dynamics) and turbulence. It originated from the Fraunhofer diffraction method. These methods are based on changes in the refractive index associated with periodic fluctuations in the density of the medium. It is a method for obtaining motion information. Fluctuations in the electron density of the plasma wave and the air density of the sound wave are the viewpoint of light, both can be treated equally because the refractive index changes periodically. It is possible. Therefore, we applied the plasma wave measurement technology to the measurement of sound waves.