Beat Notes

What happens when we add two frequencies that are not harmonically related?

The beat note comes about by adding two sinusoids that are very close in frequency.

**Figure 8:** Beat Note made by adding sinusoids at frequencies 218 Hz and 222 Hz.
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The resulting waveform shows that there is a periodic, low frequency amplitude envelope superimposed on a higher frequency sinusoid.

**Figure 9:** Waveform of a Beat Note.
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What is going on?

``Music 171: Additive Synthesis'' by Tamara Smyth, Department of Music, University of California, San Diego (UCSD).