Sometimes, when the wind blows across a long wire, a low-frequency \"moaning\" s

Question

Sometimes, when the wind blows across a long wire, a low-frequency "moaning" sound is produced. This sound arises because a standing wave is set up om the wire, like a standing wave on a guitar string.

Assume that a wire (linear density = 0.0140 kg/m) sustains a tension of 323 N because the wire is stretched between two poles that are 7.60 m apart. The lowest frequency that an average, healthy human ear can detect is 20.0 Hz. What is the lowest harmonic number n that could be responsible for the

Explanation / Answer

first calculate the speed of the wave along the wire
v = sqrt(tension/density) = sqrt(323/0.0140) = 151.89 m/s
then the length of the wire = 0.5 wavelength (node at each end)
so wavelength = 2 * 7.6 = 15.2 m
so fundamental frequency = wavespeed/wavelength = 9.99 Hz
so 20 Hz is the 20/9.99 = 2nd harmonic.

so it should be 2nd harmonic as the answer

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