Principle, verification regulations, and internal structure analysis of relevant models of sound level meters
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 according to the auditory characteristics of the human ear.
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 sound level meters in measuring 1000Hz pure tones under standard conditions, in the 1960s, sound level meters were internationally divided into two categories: 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 is a frequency characteristic that simulates the human ear's response to low intensity noise below 55 decibels; The B-weighted sound level simulates the frequency characteristics of moderate intensity noise ranging from 55 to 85 decibels; The C-weighted sound level is a characteristic of simulating high intensity noise.
Since the 1970s, some countries have introduced four classification methods, namely type 0, type 1, type 2, and type 3. Their accuracy is ± 0.4dB, ± 0.7dB, ± 1.0dB, and ± 1.5dB, respectively.
According to the different power sources used for sound level meters, they can also be divided into two types: AC type and DC type with dry batteries, and the latter can also become portable. Portable has the advantages of small size, light weight, and convenient on-site use.
It is generally composed of a microphone, amplifier, attenuator, weight 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, and is a sensor. Common types of microphones include crystal type, electret type, dynamic coil type, and capacitive type.
(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 weighting networks: A, B, and C. A-weighted sound level is a frequency characteristic that simulates the human ear's response to low intensity noise below 55 decibels; The B-weighted sound level simulates the frequency characteristics of moderate intensity noise ranging from 55 to 85 decibels; The C-weighted sound level is a characteristic of simulating high intensity noise.
(4) In order for the amplified signal to be displayed through the meter head, a detector is also needed to convert the rapidly changing voltage signal into a slower changing DC voltage signal.
