DEMONSTRATIVE EXPERIMENTS: ACOUSTICS

20. Beats

Widgets:
Two tuning-forks, multisteps osciloscope, microphone,
 
Description of experiments:
Two parallely oriented tuning-forks directed with holes to students are situated at the desk. Hitting with ruber hammer makes them pruduce a sound. After short while we mute them. After that we adjust metal ring to one side. After hitting both tuning-forks we hear sound different to  previous case. 
 
Physical problem solving:
Tuning-forks produce a tones with the same frequency. That's the reason why we hear clear tone in the first case. In the second case the frequencies differ from each other a little. Interference of these sounds results in changing volume level of heard sound - beats.

Realization notes:
Tuning -forks shouldn't touch each other.
 
Questions:
1. Where in your everyday life you can meet beats?