The principle and the introduction of the decibel meter Noise meter Sound level meter
Noise meter header response indicators
At present, 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, which is generally used to measure steady-state noise, and the measured value is the effective value.
(2) Quick. The time constant of the meter header is 125ms, which is generally used to measure unstable noise with large fluctuations and transportation noise. Fast gear approaches the human ear's response to sound.
(3) Pulse or pulse hold. The rising time of the dial is 35ms, used to measure pulse noise with a longer duration, such as punching machines, hammers, etc. The measured value is * significant value.
(4) Peak holding. The rising time of the dial is less than 20ms. It is used to measure pulse sounds with short duration, such as guns, cannons, and explosions. The measured value is the peak value, which is * the maximum value.
Classification:
Noise meters can be divided into precision noise meters and ordinary noise meters based on 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 levels.
Pulse noise meter is used to measure pulse noise, which conforms 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 a fundamental instrument in noise measurement. Noise meters generally consist of capacitive microphones, preamplifiers, attenuators, amplifiers, frequency weighting networks, and effective value indicator heads. 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 changed 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 filtering) on the signal, and then amplifies the signal to a certain amplitude through attenuators and amplifiers. It is sent to the effective value detector (or external level recorder) and provides the value of the noise level on the indicator head.
Standard weighting of noise meters
There are three standard frequency weighting networks in noise meters: A, B, and C. The A network simulates the response of the human ear to a 40 square meter pure tone in the equivalent response curve, and its curve shape is opposite to the 340 square meter equivalent response curve, resulting in significant attenuation in the middle and low frequency bands of the electrical signal. The B network simulates the response of the human ear to 70 square pure tones, causing a certain attenuation in the low frequency range of electrical signals. The C network simulates the response of the human ear to 100 square meters of pure tones, with an almost flat response throughout the entire audio frequency range. The sound pressure level measured by the noise meter through a frequency weighting network is called the sound level. Depending on the weighting network used, it is called the A sound level, B sound level, and C sound level, with units recorded as dB (A), dB (B), and dB (C).
