-Beats-

Beating is the periodic variation in intensity at a given point due to the superposition of two waves having slightly different frequencies.

The beat frequency, f is equal to

fb = f1 – f2

For example, if one tuning fork is vibrating at 438 Hz, and another is vibrating at 442 Hz, the sound wave, which is a combination of both, is 440 Hz (an A note), and the beat frequency is 4 Hz. This means that listening, you would hear that 440 Hz sound wave (an A note) go through an intensity maximum four times every second.

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