Working Principles and Component Configuration of Sound Level Meters
The inherent irregular motion and mutual repulsion of air molecules create a static force, which is called atmospheric pressure. Sound is the vibration of air molecules, and the vibrating air molecules generate additional pressure on the cross-section they pass through, which is called sound pressure. The sound pressure is much smaller than atmospheric pressure. Generally, sound pressure level is used to describe the size of sound. That is, a very small sound pressure p0=2 x 10-5 Pa is used as the reference sound pressure. The value obtained by multiplying the ratio of the measured sound pressure p to the reference sound pressure p0 by 20 is called sound pressure level, and the unit is decibels (db). Decibel (dB) is named after American telephone inventor Bell, as the unit of decibel is too large, it is used to represent 1/10 of a decibel. The calculation of decibels is not a linear proportion, but a logarithmic proportion. 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
A sound level meter is a fundamental instrument in noise measurement, typically consisting of a microphone, preamplifier, attenuator, amplifier, frequency weighting network, and effective value indicator head.
The working principle of a sound level meter is:
The sound is converted into an electrical signal by a microphone, and then the impedance is transformed by a preamplifier to match the microphone with an 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 an attenuator and amplifier, and sends it to the effective value detector (or an external level recorder). The noise level value is displayed on the indicator head.
