Practice Problem
The speed of sound waves in air is found to be 340 m/s. Determine the fundamental frequency (1st harmonic) of a closed-end air column which has a length of 67.5 cm.

Answer

Given:
v=340 m/s
L=67.5 cm = 0.675 M

 

Wavelength = 4*Length
Wavelength = 4*0.675 m
Wavelength = 2.7 m

Find:
F = ?

Diagram:

 

Speed = frequency * wavelength
frequency = speed / wavelength
frequency = (340 m/s)/(2.7 m)
frequency = 126Hz