Closely Spaced Sinusoids as
Amplitude Modulation

The previous example looks like this in the time domain:

• Over one ``beat'' of the difference frequency, the AM modulation due to ``sinusoidal interference'' is equivalent to a Hann window

• Modulation envelope is precisely sinusoidal

• In the absence of noise, and under the assumption of sinusoidal modulation (or, equivalenly, interference by one other sinusoid), all parameters can be recovered