Standing waves in air, quite analogous to the standing waves on a string, can be produced in the air column inside a cylindrical tube. An aluminum plug may be moved along the tube and the presence of the standing wave detected by listening for nodes and anti-nodes in the standing wave pattern. In this case, the excitation is provided by a small speaker driven by a function generator. The arrangement is sketched below.
frequency of the output signal
within DataStudio to 1000 Hz.
Starting with the movable piston near the speaker, move the piston away
from the end until the sound reaches a minimum.
Record the position of the piston when there is a minimum intensity. Continue to
move the piston along the tube, recording all the rest of the points along the
tube where the sound is weakest.
Average the distances between these successive points; then find the
corresponding wavelength. Use Eq.(1) to
calculate the speed of sound in air.
velocity of sound in air is known to vary with temperature as:
Compare your value of v measured for the standing wave with the one found from Eq.(3) using the % difference.