Choosing Accuracy Levels for Sound Level Meters and Noise Monitoring Devices
In the old sound level meter standard, sound level meters were categorized by accuracy class into Type 0, Type 1, Type 2 and Type 3. The new sound level meter standard will be divided into 1 and 2 according to the accuracy level of the sound level meter, they are equivalent to the old type 1 and 2, no longer have type 0 and 3. In China's environmental monitoring system in general use of type 2 (the new standard is called level 2) environmental noise measurement instruments, which is due to the relevant national standards for environmental noise measurement in the use of type 2 or more than type 2 instruments. When the national standards were first developed more than 30 years ago, the main considerations were that there were fewer Type 1 instruments at that time, as well as economic reasons. But now the situation has changed a lot, level 1 monitoring instruments have emerged in large numbers, and economically level 1 instruments are not much more expensive than level 2 instruments, generally about 30% to 50% more expensive. The performance of level 1 instruments is much better than that of level 2 instruments. For example, the accuracy, we can not simply think that the level 1 is 0.7dB (excluding measurement uncertainty, the same below), level 2 is 1.0dB, only a difference of 0.3dB. This indicator is in the specific conditions of the error, that is, in the specified reference environmental conditions (temperature +23 ℃, relative humidity of 50%, atmospheric pressure 101.325kPa), the reference level range (eg, 40 ~ 110), the reference sound pressure, the reference sound pressure, the reference sound pressure, the reference level range (eg, 40 ~ 110), the reference sound pressure, the reference sound pressure is much better than the instrument. 110), reference level range (e.g. 40~110), reference sound pressure level (e.g. 94dB), reference frequency (e.g. 1000Hz), reference direction of sound incidence (e.g. 0° incidence), and so on, the accuracy under strictly defined conditions. This is certainly not the case for actual measurements, and when any of these conditions are changed, the error caused by a Class 2 instrument is greater than that of a Class 1 instrument, and the combined difference between the two can be more than 1.0 dB.
In addition, in the new sound level meter standard, the working temperature range of level 1 sound level meter is -10℃~+50℃, the sensitivity change is not more than ±0.5dB relative to the reference temperature in this temperature range; and the working temperature range of level 2 sound level meter is 0℃~+40℃, the sensitivity change is not more than ±1.0dB relative to the reference temperature in this temperature range. Since most of the environmental noise monitoring instruments are used in the field, the environmental conditions change a lot, obviously 1 level instruments can better meet the requirements of environmental noise measurement. In China, the relevant product noise measurement standards, occupational noise pollution measurement standards basically provide for the use of 1-type noise measurement instruments, more developed countries abroad have not produced 2-level instruments. Therefore, units with the conditions should try to use level 1 instruments. It is suggested that in the future, when the relevant national standards for environmental noise are formulated, it is stipulated that the use of class 1 instruments or at least recommended to prioritize the use of class 1 instruments. It is believed that with the popularization and application of class 1 environmental noise measuring instruments, it will greatly promote the improvement of China's environmental noise monitoring level.
