Sound Level Meter - Volume Meter - Noise Meter
Sound level meter is the most basic instrument in noise measurement. The sound level meter is generally composed of a condenser microphone, a preamplifier, an attenuator, an amplifier, a frequency weighting network, and an RMS indicator. The working principle of the sound level meter is: the microphone converts the sound into an electrical signal, and then the preamplifier converts the impedance to match the microphone and the attenuator. The amplifier adds the output signal to the weighting network, performs frequency weighting on the signal (or external filter), and then amplifies the signal to a certain amplitude through the attenuator and amplifier, and sends it to the rms detector (or external level recorder) to give A value indicating the noise level above the head is displayed.
There are three standard weighting networks A, B and C in the frequency weighting network of the sound level meter. The A network simulates the human ear's response to a 40-square pure tone in an equal loudness curve. Its curve shape is opposite to the 340-square equal-loudness curve, which makes the middle and low frequency bands of the electrical signal attenuate greatly. The B network simulates the human ear's response to a 70 square pure tone, so that the low frequency band of the electrical signal has a certain attenuation. The C network simulates the human ear's response to a 100-square pure tone, with a nearly flat response over the entire audio range. The sound pressure level measured by the sound level meter through the frequency weighting network is called the sound level. Depending on the weighting network used, they are called A, B, and C levels in units of dB(A), DB(B), and dB(C).
The sound level meter can be connected to external filters and recorders to analyze the noise spectrum. The domestic ND2 precision sound level meter is equipped with an octave page interval filter, which is easy to carry to the scene for spectrum analysis.
Sound level meters can be divided into precision sound level meters and ordinary sound level meters according to their accuracy. The measurement error of the precision sound level meter is about ±1dB, and the measurement error of the ordinary sound level meter is about ±3dB. Sound level meters can be divided into two categories according to their use: one is used to measure steady-state noise, and the other is used to measure non-steady-state noise and impulse noise.
Integrating sound level meters are used to measure the equivalent sound level of unstable noise over a period of time. A noise dosimeter is also an integral sound level meter and is mainly used to measure noise exposure.
Impulse sound level meters are used to measure impulse noise. This sound level meter corresponds to the human ear's response to impulse sound and the average time of the human ear's response to impulse sound.
Fields of application of various standards
The 0-level standard is suitable for areas that require quietness, such as nursing homes, high-end villa areas, and high-end hotel areas. Suburbs, villages and other areas are subject to stricter 0 and 5dB standards.
The first-level standard applies to areas dominated by residential, cultural and educational institutions. Rural living environment can refer to the implementation of such standards.
Category 2 standards apply to mixed residential, commercial and industrial areas.
Class 3 standards apply to the industrial sector.
The fourth category of standards is applicable to areas on both sides of urban road traffic arterial roads, and areas on both sides of inland waterways that pass through urban areas. The background noise of the areas on both sides of the main and auxiliary railway lines passing through the urban area (referring to the noise level when the train does not pass) is also applicable to this type of standard.
