Purpose: To demonstrate interference of sound in a way that is similar to double-slit interference of light.

*Demonstration not currently available in CHEMP 130.

If you need this demo sooner rather than later let me know and I'll move its priority up.

Triangular arrangement of tubes having a speaker at the center of the base and a microphone where the tubes come together at the apex of the triangle; function generator; oscilloscope connected to the output of the the microphone. One leg of the triangular tube telescopes so that its length can be changed.

Discuss the conditions for constructive interference at the position of the microphone. Turn on the function generator set for about 2000 Hz, and find points of constructive and destructive interference by observing the loudness level and by the display on the oscilloscope. Show that, for constructive interference, the length of one side can be changed by a whole number of wavelengths to return to constructive interference. Measure the length change for one side between positions of maxima. Use this information to calculate the speed of sound (or some other permutation of such a calculation).

References:

Manual: None