Background noise can cause considerable error in measurement when its intensity is close to that of a particular sound source of interest. When it is not possible

to eliminate or reduce the background noise, use the curve shown in Figure 4 to correct for the effect of the background noise on the measurement. For

example, if the background noise is 45 dB and the sound of interest measures 51 dB, the difference between measurement and background noise is 6 dB. From

Figure 4, for a 6 dB difference, 1.3 dB should be subtracted from the measurement. The correct measurement is therefore 51 dB- 1.3 dB= 49.7 dB.

Sound Examiner SE-400 Series

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