Principle and Introduction of Noise Meter and Sound Level Meter
At present, the noise meters used for measuring noise can be divided into four types based on sensitivity:
(1) Slow. The time constant of the meter head is 1000 ms, usually used to measure steady-state noise, and the measured value is the effective value.
(2) Quick. The time constant of the meter head is 125ms, which is generally used to measure unstable noise and transportation noise with significant fluctuations. The fast gear approaches the human ear's response to sound.
(3) Pulse or pulse hold ". The rise time of the watch needle is 35ms, used to measure pulse noise with a longer duration, such as punching machines, press hammers, etc. The measured value is the maximum effective value.
(4) Peak hold ". The rise time of the watch needle is less than 20ms. It is used to measure pulse sounds with a short duration, such as guns, guns, and explosions. The measured value is the peak, which is the maximum value.
Classification:
Noise meters can be divided into precision noise meters and ordinary noise meters based on their accuracy. The measurement error of a precision noise meter is about 1dB, while that of a regular noise meter is about 3dB. Noise meters can be divided into two categories according to their purpose: one is used to measure steady-state noise, and the other is used to measure unstable noise and pulse noise.
An integral noise meter is used to measure the equivalent sound level of unstable noise over a period of time. A noise dosimeter is also an integral type noise meter, mainly used to measure noise exposure.
Pulse noise meter is used to measure pulse noise, which corresponds to the response of the human ear to pulse sound and the average time of the human ear's response to pulse sound.
Working principle:
A noise meter is the most basic instrument in noise measurement. A noise meter generally consists of a capacitive microphone, preamplifier, attenuator, amplifier, frequency weighting network, and effective value indicator head. The working principle of a noise meter is that the sound is converted into an electrical signal by a microphone, and then the impedance is converted by a preamplifier to match the microphone with the attenuator. The amplifier adds the output signal to the weighting network, performs frequency weighting (or external filter) on the signal, and then amplifies the signal to a certain amplitude through an attenuator and amplifier, and sends it to the effective value detector (or external level recorder). The noise level value is given on the indicator head.
