Demonstration consists of a pair of tuning forks mounted on wooden boxes which are open on one end. One of the tuning forks has a pair of adjustable weights which attach to the forks.

This demonstration can also be run using a pair of organ pipes (where one of them is adjustable to be very close to the other) or a pair of speakers with separate adjustable frequency generators.

Demonstration of the constructive and destructive interference ('beating') observed when two different (but very close) frequencies are played together.

Pair of organ pipes, two tuning forks, oscillators, or amplifiers and horn speakers

• Two organ pipes, one with a variable frequency adjustment are sounded together. By moving the frequency adjustment of one pipe to obtain a frequency close to the other pipe will result with beats.

• Two identical tuning forks on resonance boxes should be placed on the demonstration bench so that the open ends of the boxes are angled to face the audience. If one fork is now damped slightly with a damping piece attached to it, beats will be heard.

• Two oscillators with their own speakers are driven producing two separated notes. Oscillator frequencies can be read off and the frequency of the beats heard matched approximately to the difference in frequency of the two oscillators. Providing the speakers and oscillators are nearly identical, an oscilloscope can be connected to show how close the frequencies are to each other.