The greater the mass of clay added, the lower the frequency of the fork. Strike each tuning fork and listen for beats.

To show beats, take a lump of clay (about half the amount supplied at first) and stick it to the tine of the fork near the top. (You might want to focus the projection camera on the apparatus for better visibility.) An erratic movement of the ping-pong ball can be seen. Place the stand holding the ping-pong ball in such a position as to make the ball just lightly touch the tine of the fork. Then place the boxes so that they face each other, open end to open end. If both forks are struck simultaneously, beats can clearly be heard.ĭirections: Strike each tuning fork to show how the resonance enhances the sound. The mass loading will cause a reduction in frequency of that fork. One can also demonstrate beats by attaching a lump of clay to one tine of one of the forks. The ping-pong ball will bounce back and forth indicating that the fork is vibrating. When the one box is placed such that its opening is a few centimeters from the others opening, striking one tuning fork sets up a sympathetic vibration in the other, which can be shown by having a ping-pong ball, attached to a thread, lightly touch the second fork. When the tuning fork is struck, the sound is amplified by the resonance occurring in the box.

Two identical wooden boxes, open at one end, have identical tuning forks attached at the center of the top of the box.

Resonance tuning forks