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INDUSTRIAL GENERATOR SETS — APPLICATION & INSTALLATION MANUAL — REV. #4 (09/07/07) — PAGE 29
ENVIRONMENTAL CONSIDERATIONS — dB(A)
Adding Additional Sound Sources
The noise level at a given location is the sum of the noise
levels from all sources, including reflecting sources. For
example, the noise level in a free field along side of two
identical generator sets would be double the noise level of
either set when both sets are running. A doubling of the
noise level is represented as an increase of approximately
3 dB(A). In this case, if the noise level from either set is
measured as 70 dB(A), the expected result of the combined
generators would be 73 dB(A) when both units are running.
Figure 3. dB(A) Comparison Chart
Alternatively, the following formula can be used to add
sound pressure levels measured in dB(A):
Figure 3 below estimates the noise level from multiple
noise sources:
1. To find the difference in dB(A) between two of the
sources (any pair), locate the dB(A) difference value
on the horizontal scale as shown by the horizontal arrow.
Add this value to the larger dB(A) value of the pair.
2. Repeat Step 1 between the value just determined and
the next value. Keep repeating the process until all
noise sources have been accounted for.