Principles, Verification Regulations and Internal Structure Analysis of Related Sound Level Meter Models
A noise meter, also known as a sound level meter, is an instrument that can approximately measure the noise level of industrial noise, household noise, and traffic noise based on human auditory characteristics.
Noise level refers to the sound pressure level (dB) or loudness level (phon) measured by a sound level meter and corrected for auditory perception.
According to the accuracy of measuring 1000Hz pure tones with a sound level meter under standard conditions, in the 1960s, sound levels were classified into two categories internationally: precision sound level meters and ordinary sound level meters.
Our country also adopts this method. There are generally three types of noise weighting networks: A, B, and C. A-weighted sound level simulates the frequency characteristics of low-intensity noise below 55 decibels for the human ear; The B-weighted sound level simulates the frequency characteristics of moderate intensity noise ranging from 55 to 85 decibels; C-weighted sound level is a characteristic of simulating high-intensity noise.
Since the 1970s, some countries have introduced four types of classification, namely Type 0, Type 1, Type 2, and Type 3. Their accuracies are ± 0.4dB, ± 0.7dB, ± 1.0dB, and ± 1.5dB, respectively.
According to the different power sources used in the sound level meter, it can also be divided into two types: AC type and DC type sound level meters using dry batteries, the latter of which can also be portable. Portable has the advantages of small size, light weight, and convenient on-site use.
It generally consists of a microphone, amplifier, attenuator, weighting network, detector, indicator head, and power supply.
(1) A microphone is a device that converts sound pressure signals into voltage signals, also known as a microphone or sensor. Common types of microphones include crystal, electret, moving coil, and capacitive.
(2) Many popular domestic and imported amplifiers and attenuators currently use two-stage amplifiers in amplification circuits, namely input amplifiers and output amplifiers, which amplify weak electrical signals.
(3) There are generally three types of weighted networks: A, B, and C. A-weighted sound level simulates the frequency characteristics of low-intensity noise below 55 decibels for the human ear; The B-weighted sound level simulates the frequency characteristics of moderate intensity noise ranging from 55 to 85 decibels; C-weighted sound level is a characteristic of simulating high-intensity noise.
(4) In order to display the amplified signal through the meter, detectors and indicator heads are also required to convert rapidly changing voltage signals into slower changing DC voltage signals.
