Beats: Feynman's Physics Explained
Add two sound waves of slightly different frequencies and you get a wave at the average frequency whose loudness pulses up and down. Those pulses are 'beats,' and their rate is the difference of the two original frequencies. This interference in time is not unique to sound — it is a general property of waves and is the principle behind AM radio.
The big idea
Two close frequencies combine into a slow throbbing beat.
Think about it
Piano tuners listen for beats between a note and a reference tone. Why does the throbbing slow down as the note gets in tune?
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