FAQ-e014

FAQ-E014: What is the background noise? Its influence?


[Answer]

The background noise is a sound that exists in a certain place other than the target sound when considering a specific sound.

In the case of measuring the noise level of a specific steady noise, it may be affected by the background noise.


When measuring the noise level, if the difference between the indicated value of the sound level meter with and without the noise is 10 dB or more, the influence of the background noise can be almost ignored.


However, when it is less than 10 dB, it cannot be ignored, and the noise level of only steady noise can be estimated by correcting the following table. Note that this correction is for stationary noise and cannot be applied when the background noise level fluctuates. The difference from the background noise level must be at least 3 dB.


Background noise level correction (unit: dB)

# Measurement value difference : Correction value (unit: dB)
　　　 　3　 　　　　　　 　: -3.0
　　　 　4　 　　　　　　 　: -2.3
　　　 　5　 　　　　　　 　: -1.7
　　　 　6　 　　　　　　 　: -1.25
　　　 　7　 　　　　　　 　: -0.95
　　　 　8　 　　　　　　 　: -0.75
　　　 　9　 　　　　　　 　: -0.60
　　　　10　 　　　　　　 　: -0.45

* Note: ISO 1996-1 (JIS Z 8731: 1999 “Description and measurement of environmental noise”)

For example, if a certain machine is measured to be 55 dBA and the background noise when it is stopped is measured to be 50 dBA. Since the level difference is 5 dB, the level is estimated to be 53.3 dBA.





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