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Unified Engineering Spring 2004
Fluids Problems F15
F15. Our analysis for determining the speed of sound assumed that the sound wave had
infinitesimal strength. But for the 120 dB sound waves produced by Linkin Park near the
stage, this assumption may be suspect.
a) One suitable definition of sound dB level is:
∆p
dB = 20 log10 20 × 10−6 Pa
where ∆p is a pressure variation caused by an average passing sound wave. Treating this
sound wave as a shock wave, determine its propagation Mach number into still air.
Hint: Put the propagating-shock situation into the shock’s frame of reference.
b) Determine the temperature fluctuations associated with the passing waves. Would you
say Linkin Park makes strong or wimpy shock waves?
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