Finding the Speed of Sound Using a Resonance Pipe
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Concept
When a pipe is partially submerged in water, the water closes one end of the pipe while the other end remains open. If the length of the pipe from the top to the water level is just the right length, a sound wave in the pipe will resonate as the sound reflects off of the water repeatedly, that is, a standing wave is produced in the pipe. There are several lengths at which a pipe will resonate, producing harmonics.
Procedure
- Place the small pipe inside the large, water-filled pipe, submerging the small pipe as far as it will go.
- Strike a tuning fork and place it above the small pipe as shown, lifting the pipe slowly until you hear the first harmonic.
- Measure the length of the small pipe from the top to the water level.
- The standing wave in the pipe is represented by the pattern shown in the pipe. What fraction of a wavelength is in the pipe?
- Knowing the length of the pipe above the water, and the fraction of a wavelength that fits in this pipe, calculate the wavelength of the sound wave in meters.
- Knowing the wavelength and frequency of your sound wave, calculate the speed of sound.
- Repeat your measurements for the next harmonic, shown at the right, and measure the speed of sound again. Do you get the same value for the speed of sound?
