What exactly is the microphone part of a sound level meter?
The receiving part of the sound level meter is the microphone. It converts the acoustic signal into an electrical signal, and after amplification, filtering, attenuation, weighting and a certain degree of circuit damping, it can give the quantitative indication of the measured noise according to the four standard classifications of fast, slow, pulse and hold.
The microphone converts the sound into an electrical signal, and the impedance is transformed by the preamplifier to match the microphone to the attenuator. The amplifier adds the output signal to the weighting network, performs frequency weighting on the signal (or an external filter), and then amplifies the signal to a certain amplitude through the attenuator and the amplifier, sends it to the RMS detector, and gives the value of the noise level on the indicator meter.
A microphone is a device that converts a sound pressure signal into a voltage signal, also known as a microphone, and it is a sensor of a sound level meter. Common microphones are crystal, electret, moving coil and condenser.
1. The moving coil microphone is composed of a vibrating diaphragm, a moving coil, a permanent magnet and a transformer. The vibrating diaphragm begins to vibrate after being subjected to sound wave pressure, and drives the movable coil installed with it to vibrate in the magnetic field to generate an induced current. The current varies according to the magnitude of the acoustic pressure on the vibrating diaphragm. The greater the sound pressure, the greater the current generated, and the smaller the sound pressure, the smaller the current generated.
2. The condenser microphone is mainly composed of a metal diaphragm and metal electrodes that are close together, which is essentially a flat plate capacitor. The metal diaphragm and the metal electrode constitute the two plates of the plate capacitor. When the diaphragm is subjected to sound pressure, the diaphragm deforms, which changes the distance between the two plates, thus changing the capacitance and the voltage in the position measurement circuit, realizing the function of converting the sound pressure signal into a voltage signal. Condenser microphone is an ideal microphone in acoustic measurement. It has the advantages of large dynamic range, flat frequency response, high sensitivity and good stability in general measurement environment, so it is widely used. Since the output impedance of the condenser microphone is very high, it is necessary to perform impedance transformation through the preamplifier. The preamplifier is installed inside the sound level meter near the place where the condenser microphone is installed.
