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Phy101 lo4,l2 f,cindyl
1. LO4. Sound and Intensity
A student is trying to listen to a sound source from a radio, which is put at a 100
m distance away; please find what the intensity like at a distance when its power
is 80W. Show calculation.
Answer: 88 dB, 6.37 *10^(-4) W/m^2
Explanation:
1) The equation we use is I=P/A (power of the source divide by the area,
which the sound spread, and the area which the sound spread is spherical
area =4pi r^2); from this, we can generate the formula to I=P/4pi r^2
2) Plug in number: I=P/4pir^2=80/4pi(100)^2=6.37 *10^(-4) W/m^2
3) Convert to dB: I in dB=10log I/I0=10 log (6.37 *10^(-4))/10^(-12)
W/m^2=88dB
4) Therefore, person standing 100m away, form a source of 80w, produces
the sound intensity of 88 dB