Civil Engineering MCQAE Level Civil Engineering
If two independent noise sources each produce a sound pressure level of 60 dB, the combined level is:
Environmental EngineeringNoise Decibel AdditionMEDIUM
Choose the correct answer
A
120 dB
B
63 dB
C
60 dB
D
90 dB
Correct Answer
B. 63 dB
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Decibels are added logarithmically: L_total = 10 log10(10^(L1/10) + 10^(L2/10)). For two equal sources of 60 dB: L_total = 10 log10(2 x 10^6) = 10(6 + log10 2) = 10(6 + 0.301) = 63.01 dB. Equal sources add about 3 dB to the higher level.
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