پرانے آواز سطح میٹر معیاری ٪ 2c میں آواز سطح میٹر کو ٹائپ میں تقسیم کیا گیا ہے 7 بی ٪ 7 بی ٪ 7 بی ٪ 7 بی 7 بی 7 بی 7 بی 7 بی 7 ڈی ٪ 7 ڈی ٪ 2 سی ٹائپ 1٪ 2 سی ٹائپ 1٪ 2 سی ٹائپ 1٪ 2 سی ٹائپ 3 کے مطابق نو ٹائپ 0 اور ٹائپ 3 اب ہیں۔ میرے ملک٪27s ماحولیاتی مانیٹرنگ سسٹم٪2c ٹائپ 2 (نیا معیاری جسے لیول 2 کہا جاتا ہے) ماحولیاتی شور پیمائش عام طور پر استعمال کیے جاتے ہیں۔ یہ کیونکہ متعلقہ قومی معیار کے لیے ماحولیاتی شور پیمائش ٹائپ 2 یا استعمال کی ضرورت ہوتی ہے۔
More than 3{{10}} years ago, when the national standards were formulated, the main considerations were the lack of type 1 instruments at that time, as well as economic reasons. But the current situation has changed a lot. Level 1 monitoring instruments have emerged in large numbers. Economically, level 1 instruments are not much more expensive than level 2 instruments, generally about 30 percent to 50 percent more expensive. Class 1 instruments perform much better than Class 2 instruments. For example, accuracy, we can't simply think that level 1 is 0.7dB (not including measurement uncertainty, the same below), and level 2 is 1.0dB, only a difference of 0.3dB. This indicator is the error under specific conditions, that is, the accuracy under strict conditions such as the specified reference environmental conditions (air temperature plus 23 degree , relative humidity 50 percent , 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 incident direction (such as 0 degree incident) and so on. Of course, this condition will not be in the actual measurement, and when any of the conditions is changed, the error caused by the second-level instrument is larger than that of the first-level instrument, and the error difference between the two may be more than 1.0dB.
In addition, in the new sound level meter standard, it is required that the operating temperature range of the first-class sound level meter is -10 degree ~ plus 50 degree , and the sensitivity change relative to the reference temperature within this temperature range is not more than ±0.5dB; while the operating temperature range of the second-class sound level meter is 0 degree ~ plus 40 degree , and the sensitivity change relative to the reference temperature within this temperature range is not more than ±1.0dB. Since most 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. In my country's relevant product noise measurement standards and occupational noise pollution measurement standards, Type 1 noise measuring instruments are basically stipulated, and relatively developed countries in foreign countries have not produced Level 2 instruments. Therefore, qualified units should try to use level 1 instruments. It is suggested that when the national standards on environmental noise are formulated in the future, the use of Class 1 instruments is stipulated or at least Class 1 instruments are recommended to be preferred. It is believed that with the popularization and application of Class 1 environmental noise measuring instruments, it will greatly promote the improvement of the environmental noise monitoring level in our country.
