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The sound power l evel of an out door nondirectional point source is 90 dB. Considering an atmospheric impedance of 400 rayls, the sound pressure level at 10 m distance from the source is _______ dB.
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- 58 to 60
- 68 to 70
- 78 to 80
- 88 to 90
Correct Option: A
58 to 60 
Putting values of Lw = 90, r = 10 m, Lp = 59,00 dB
(No role of atmospheric impedance)
