As people sing in church, the sound level everywhere inside is 122 dB. No sound
ID: 1401321 • Letter: A
Question
As people sing in church, the sound level everywhere inside is 122 dB. No sound is transmitted through the massive walls, but all the windows and doors are open on a summer morning. Their total area is 22.5 m2. (Enter only the answers in the input boxes separately given.)
(a) How much sound energy is radiated in 26.5 min?
1. ( Enter in box 1) J
(b) Suppose the ground is a good reflector and sound radiates uniformly in all horizontal and upward directions. Find the sound level 1.4km away.
2. ( Enter in box 2)
Explanation / Answer
first we will convert 122db to wb/m^2
10^(dB level/10) and multiply by 10^-12 W/m^2
so we get 1.58W/m^2
Intensity=power/Area
1.58*22.5 m2=power
35.55watt=Power
energy=power*time
26.5 minutes=1590sec
Energy=35.55*1590
Energy=56445J--answer to a
b) I = P/4pir^2.
=35.5/4*3.14*1400^2
=0.00000144
I=1.44*10^-6
B = 10 log(1.44x10^-6/10^-12)
B=61.5db--answer to b
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