Principle of operation and structure of a sound level meter
The inherent irregular movement and mutual repulsion of air molecules will form a static force, and this pressure is atmospheric pressure. Sound is the vibration of air molecules. The vibrating air molecules will produce additional pressure on the cross section through which it passes. This additional pressure is called sound pressure. The sound pressure is much smaller than the atmospheric pressure. Generally, the sound pressure level is used to describe the size of the sound, that is, a very small sound pressure p0=2х10-5 Pa is used as the reference sound pressure, and the sound pressure p to be measured is The value obtained by taking the common logarithm of the ratio to the reference sound pressure p0 and multiplying by 20 is called the sound pressure level, and the unit is decibel (db). Decibel (dB) is named after the American telephone inventor Bell. Because the unit of bel is too large, decibel is used, which represents 1/10 bel. The operation of decibels is not linearly proportional, but logarithmic. When using decibels to describe sound, the frequency needs to be given at the same time.
The working principle and composition of a sound level meter
The sound level meter is the most basic instrument in noise measurement. It generally consists of a microphone, preamplifier, attenuator, amplifier, frequency weighting network and effective value indicator meter.
The working principle of the sound level meter is:
The microphone converts the sound into an electrical signal, and then the preamplifier changes the impedance to match the microphone and the attenuator. The amplifier adds the output signal to the weighting network, performs frequency weighting on the signal (or external filter), and then amplifies the signal to a certain amplitude through the attenuator and amplifier, and sends it to the effective value detector (or external voltage detector). Level recorder), giving the value of the noise level on the indicator head.
