(I) What is the sound level of a sound whose intensity is 1.5 times 10^-6 W/m^2?
ID: 1561987 • Letter: #
Question
(I) What is the sound level of a sound whose intensity is 1.5 times 10^-6 W/m^2? (II) You are trying to decide between two new stereo amplifiers. One is rated at 75 W per channel and the other is rated at 120 W per channel. In terms of dB, how much louder will the more powerful amplifier be when both are producing sound at their maximum levels? (II) If two firecrackers produce a combined sound level of 85 dB when fired simultaneously at a certain place, what will be the sound level if only one is exploded?Explanation / Answer
1) I = intensity = 1.5*10-6 W/ m2
sound level in decibel (dB)
L = 10 log10 [ I/ I0]
I0 = threshold of hearing = 1012 Watt/m2
L = 10*log10 [ 1.5*10-6 / 10-12]
L= 61.76 dB
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2) P1 = 75 W
P2 = 120 W
intensity level of first ,I1 = 10 log( P1/ I0)
I2 = 10 log( P2/I0)
difference in intensity ( dB) levels = I2 - I1
= 10 log( 120/ I0) - 10 log ( 75 / I0)
= 10 log ( [120/ Io ] / [75/I0] ( log m - log n = log(m/n)
= 10 log( 120 / 75 = 2.041 dB
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