Engineering Board Exam Reviewer · Environmental Engineering · hard
With a machine running, the noise level is 95 dB. With the machine off, the background level is 88 dB. What noise level is due to the machine alone?
- 7.0 dB
- 94.0 dB
- 95.0 dB
- 91.5 dB
Answer
B. 94.0 dB
Solution
Lmachine = 10 (109.5 - 108.8) = 94.0 dB. (Decibels cannot be subtracted directly.)
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