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gmmstr827
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Homework Statement
Two loudspeakers are placed 3.00 m apart. They emit 494-Hz sounds, in phase. A microphone is placed 3.20 m distant from a point midway between the two speakers, where an intensity maximum is recorded. (a) How far must the microphone be moved to the right to find the intensity minimum? (b) Suppose the speakers are reconnected so that the 494-Hz sounds they emit are exactly out of phase. At what positions are the intensity maximum and minimum now?
See image for clearer description:
http://i29.photobucket.com/albums/c261/gmmstr827/speakersmic.jpg
Homework Equations
Sound travels in air at 20° C at a rate of:
v = 343 m/s
b = beat
Γ_b = v / f_b
f_b = |f_1 - f_2 | <<< (absolute value)
f_1 = v/Γ_1
f_2 = v/Γ_2
The Attempt at a Solution
a)
f_b = 494 Hz
Γ_b = v / f_b
Γ_b = (343 m/s) / (494 Hz) = 0.69 m per wavelength beat
Moving the microphone half that distance would put it in the intensity minimum zone, so:
0.69 m / 2 = 0.35 m
The microphone must be moved about 0.35 meters to the right to reach an intensity minimum.
b)
This simply swaps the previous mins/maxes, therefore putting the default microphone position in a minimum, and about .035 m to the right would be a maximum.
^^^ Is this all correct? Thank you!
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