Introduction to Sound Level Meter Microphones
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) A moving coil microphone is composed of a vibrating diaphragm, a movable 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.
Briefly describe the classification of sound level meters
The sound level meter can be connected with an external filter and recorder to perform spectrum analysis on the noise. The domestic ND2 precision sound level meter is equipped with an octave page filter, which is easy to carry to the scene and do spectrum analysis.
Sound level meters can be divided into precision sound level meters and ordinary sound level meters according to their accuracy. The measurement error of a precision sound level meter is about ±1dB, and that of an ordinary sound level meter is about ±3dB. Sound level meters can be divided into two categories according to their uses: one is used to measure steady-state noise, and the other is used to measure unsteady-state noise and impulse noise.
Integrating sound level meters are used to measure the equivalent sound level of unsteady noise over a period of time. Noise dosimeter is also an integrating sound level meter, mainly used to measure noise exposure.
Impulse sound level meter is used to measure impulse noise. This sound level meter conforms to the human ear's response to impulse sound and the average time of human ear's response to impulse sound.
