Refers to the ratio of the open circuit voltage of the microphone to the sound pressure acting on its diaphragm. In fact, the microphone will inevitably cause sound field scattering in the sound field, so there are two definitions of sensitivity. One is the sound pressure actually acting on the diaphragm, called the sound pressure sensitivity, and the other refers to the sound pressure of the sound field where the microphone is not placed in the sound field, called the sound field sensitivity, where the sound field sensitivity is divided into free field sensitivity and diffusion Field sensitivity. Usually, the microphone for recording gives the sound pressure sensitivity, and the microphone for measurement gives the sound pressure or sound field sensitivity depending on the type of application.
The unit of sensitivity is Volt/Pa (Volt/Pascal, V/Pa), which is usually expressed by the sensitivity level, and the reference sensitivity is 1V/Pa.
The frequency response of the microphone
It means that when the microphone receives sounds of different frequencies, the output signal will be amplified or attenuated as the frequency changes. The most ideal frequency response curve is a horizontal line, which represents that the output signal can directly present the characteristics of the original sound, but this ideal situation is not easy to achieve. Generally speaking, the frequency response curve of a condenser microphone will be flatter than that of a moving coil. The frequency response curve of common microphones is mostly high and low frequency attenuation, while the middle and high frequencies are slightly amplified; low frequency attenuation can reduce the interference of low frequency noise around the recording environment.
In the frequency response graph, the horizontal axis is frequency, and the unit is hertz. In most cases, it is represented by logarithms; the vertical axis is sensitivity, and the unit is decibels.
The impedance of the microphone
In the microphone specifications, the impedance value (in ohms) is listed. According to the Maximum Power Transfer Theorem, when the load impedance matches the microphone impedance, the power of the load will reach the maximum value. However, in most cases of impedance mismatch, the microphone can still be used, so this specification has not received much attention. Generally speaking, low impedance is lower than 600 ohms; medium impedance is between 600 and 10,000 ohms; high impedance is higher than 10,000 ohms.