The sensitivity of a microphone refers to the ratio of the open circuit voltage of the microphone to the sound pressure acting on its diaphragm. In fact, microphones inevitably cause sound field scattering in the sound field, so there are two definitions of sensitivity. One is the actual sound pressure acting on the diaphragm, which is called the sound pressure sensitivity, and the other is the sound pressure of the sound field where the microphone is not placed in the sound field, which is called the sound field sensitivity. The sound field sensitivity is divided into free field sensitivity and diffusion field sensitivity. The sound pressure sensitivity is usually given by a recording microphone, and the measurement microphone gives sound pressure or sound field sensitivity depending on the type of application.