Concepts

Beats

Overview

Two identical tuning forks mounted on resonance boxes are struck with rubber mallets to show they have identical tones. A small piece of putty is added to one tuning fork to alter it's frequency. When the tuning forks are struck again, beats can be heard due to the small frequency difference.

Details

Equipment

• [2] Identical tuning forks mounted on resonance boxes
• [2] Rubber mallets
• [1] Small piece of putty

Classroom Assembly

1. Place the rubber mallets and tuning forks on the lectern with the open ends of the resonance boxes facing the audience. 
2. Place a small piece of putty next to one tuning fork.

Important Notes

• Details of the tuning forks can't be seen in a large lecture hall, but the sound can be clearly heard.

Script

1. Hit both tuning forks with the rubber mallets. Note that they have identical tones.
2. Place a small piece of putty on top of one tuning fork.
3. Hit both tuning forks again. Note the beats.
4. Increase the size of the putty piece.
5. Hit both tuning forks again. Note the difference in beat frequency.

Additional Resources