Selection of accuracy levels for sound level meters and noise monitoring instruments
The sound level meter standard divides the sound level meter into level 1 and level 2 according to its accuracy level, which are equivalent to the old types 1 and 2, and there are no longer types 0 and 3. In China's environmental monitoring system, Type 2 (referred to as Level 2 in the new standard) environmental noise measurement instruments are commonly used. This is because the relevant national standards for environmental noise measurement stipulate the use of Type 2 or above instruments.
When formulating national standards more than thirty years ago, the main considerations were the scarcity of Type 1 instruments and economic reasons at that time. However, the current situation has greatly changed, with a large number of Level 1 monitoring instruments emerging. Economically, Level 1 instruments are not much more expensive than Level 2 instruments, usually around 30% to 50% more expensive. The performance of Level 1 instruments is much better than that of Level 2 instruments. For example, accuracy, we cannot simply assume that level 1 is 0.7dB (excluding measurement uncertainty, the same below), and level 2 is 1.0dB, with only a difference of 0.3dB. This indicator is the error under specific conditions, that is, the accuracy under strictly specified conditions such as reference environmental conditions (temperature+23 ℃, relative humidity 50%, atmospheric pressure 101.325kPa), reference level range (such as 40-110), reference sound pressure level (such as 94dB), reference frequency (such as 1000Hz), reference sound incidence direction (such as 0 ° incidence), etc. In actual measurement, of course, this condition will not be the case, and when any of these conditions change, the error caused by Level 2 instruments is greater than that of Level 1 instruments. Overall, the error difference between the two may be over 1.0dB.
In addition, in the new standard for sound level meters, it is required that the operating temperature range of level 1 sound level meters is -10 ℃~+50 ℃, and the sensitivity change relative to the reference temperature within this temperature range should not exceed ± 0.5dB; The working temperature range of the Level 2 sound level meter is 0 ℃~+40 ℃, and the sensitivity change relative to the reference temperature within this temperature range is not more than ± 1.0dB. Due to the fact that most environmental noise monitoring instruments are used on-site and the environmental conditions vary greatly, it is evident that Level 1 instruments can better meet the requirements of environmental noise measurement. In China, the relevant product noise measurement standards and occupational noise pollution measurement standards basically stipulate the use of Type 1 noise measurement instruments, while more developed countries abroad no longer produce Level 2 instruments. Therefore, units with conditions should choose Level 1 instruments as much as possible. It is recommended to specify the use of Level 1 instruments or at least prioritize the use of Level 1 instruments when formulating national standards for environmental noise in the future. I believe that with the promotion and application of Level 1 environmental noise measurement instruments, it will greatly promote the improvement of China's environmental noise monitoring level.
