Selection of accuracy levels of sound level meters and noise monitoring instruments
In the old sound level meter standards, sound level meters are divided into type 0, type 1, type 2 and type 3 according to the accuracy level. The new sound level meter standard divides sound level meters into Level 1 and Level 2 according to the accuracy level. They are equivalent to the old Type 1 and Type 2, and there are no longer Type 0 and Type 3. Type 2 (called Level 2 in the new standard) environmental noise measuring instruments are commonly used in my country's environmental monitoring systems. This is because the relevant national standards for environmental noise measurement stipulate the use of Type 2 or above instruments. When the national standards began to be formulated more than 30 years ago, the main considerations were the lack of Type 1 instruments at that time and economic reasons. But now the situation has changed a lot. Level 1 monitoring instruments have emerged in large numbers. Economically speaking, 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, for accuracy, we cannot simply think that level 1 is 0.7dB (excluding measurement uncertainty, the same below) and level 2 is 1.0dB, with a difference of only 0.3dB. This indicator is the error under specific conditions, that is, under the specified reference environmental conditions (air temperature +23°C, relative humidity 50%, atmospheric pressure 101.325kPa), reference level range (for example, 40~110), reference sound pressure level ( Accuracy under strictly specified conditions such as 94dB), reference frequency (e.g. 1000Hz), reference sound incident direction (e.g. 0° incident), etc. Of course, this condition will not be used during actual measurement. When any of the conditions changes, the error caused by the Level 2 instrument will be larger than that of the Level 1 instrument. In total, the error difference between the two may be more than 1.0dB.
In addition, in the new sound level meter standard, the operating temperature range of level 1 sound level meters is required to be -10℃~+50℃, and the sensitivity change relative to the reference temperature within this temperature range is not greater than ±0.5dB; while level 2 sound level meters The operating temperature range of the level meter is 0℃~+40℃. Within this temperature range, the sensitivity change relative to the reference temperature is not greater than ±1.0dB. Since most of the environmental noise monitoring instruments are used on-site and the environmental conditions change greatly, it is obvious that level 1 instruments can better meet the requirements of environmental noise measurement. my country's relevant product noise measurement standards and occupational noise pollution measurement standards basically stipulate the use of type 1 noise measuring instruments. More developed countries abroad no longer produce level 2 instruments. Therefore, qualified units should try to use level 1 instruments. It is recommended that when national standards for environmental noise are formulated in the future, the use of Class 1 instruments should be stipulated or at least the use of Class 1 instruments should be recommended first. It is believed that with the promotion and application of level 1 environmental noise measuring instruments, the level of environmental noise monitoring in our country will be greatly improved.
