At a rock concert, a dB meter registered 135 dB when placed 2.2 m
in front...
At a rock concert, a dB meter registered 135 dB when placed 2.2 m
in front of a loudspeaker on the stage.
1) What was the power output of the speaker, assuming uniform
spherical spreading of the sound and neglecting absorption in the
air?
2) How far away would the sound level be a somewhat reasonable 95
dB?
Solutions
Expert Solution
Concepts and reason
The concept required to solve the given problem is power and intensity of sound.
Initially, use the expression of sound intensity level to find the intensity of sound in W/m2 . Use the expression of power output i.e. P=IA , find the area of uniform sphere, substitute the values in the equation and find output power.
In the next part, first find the intensity of sound. Use the same power and intensity to find the distance value r.
Fundamentals
The expression to measure sound intensity level is decibels is given as follows:
β=10log10(I0I)
Here, I is the intensity of sound and I0 is the reference intensity.
The power output of the speaker is calculated as follows:
P=IA
Here, I is the intensity and A is the area.
(1)
Substitute 135 dB for β and 10−12W/m2 for I0 in equation β=10log10(I0I1) and find I1 .
At a rock concert, a dB meter registered 130 dB when placed 2.2
m in front of a loudspeaker on the stage.
a. What was the power output of the speaker, assuming uniform
spherical spreading of the sound and neglecting absorption in the
air?
b. How far away would the sound level be a somewhat reasonable
95 dB ? answer with units
At a rock concert, a dB meter registered 125 dB when placed 2.9
m in front of a loudspeaker on the stage. The intensity of the
reference level required to determine the sound level is
1.0×10−12W/m2.
A)What was the power output of the speaker, assuming uniform
spherical spreading of the sound and neglecting absorption in the
air?
B) How far away would the sound level be 86 dB ?
When you stand 1 meter away from the loudspeakers for a rock
band, it is just on the threshold of pain (approximately 120 dB).
How far away should you stand to reduce the sound intensity level
to 60 dB, equivalent to an everyday normal conversation?
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0.569
0.385
0.157
0.689
0.265
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