Consider a tuning fork tuned to middle C, . If the sound intensity (proportional to the energy of oscillation) when the tuning fork is struck decreases by a factor of 4 in 6 seconds, what is the quality factor of the tuning fork to the nearest integer?
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If the sound intensity decreases by a factor of 4 in 6 seconds, then:
e − 6 b / m = 4 1 .
where b and m are the damping constant and mass of the tuning fork respectively treating it as a damped harmonic oscillator .
Taking the logarithm of both sides and rearranging,
b m = lo g 4 6 .
By the definition of the quality factor:
Q = b m ω ,
where ω is measured in radians. Since ω = 2 6 1 . 6 Hz , find:
Q = lo g 4 6 ( 2 6 1 . 6 ) ( 2 π ) ≈ 7 1 1 4 .