Spectral Formula of a Waveform
For the curious: the spectral formula of a waveform gives a simple relationship between the partial number and its amplitude (remember, we know its frequency from the Fourier theorem).
For example, the formula for a square wave is an amplitude of 1/n, when n is odd, or 0, when n is even.
Using the formula, we can compute the following partial strengths for a square wave:
and so on.
There are some other simple waveforms whose formulae are well known:
Surprisingly, as we mentioned in Section 1.4, symmetrical waveforms (like the square and triangle) have no even partials.
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