Fourier analysis of echoes yields alternating strong and weak spectral bands

Evidence

At low frequency, f1, the cosine in the Fourier analysis of the signal is long wavelength, and the signal multiplied by the cosine adds up all the echoes with the same sign (first inset, figure 12.3), giving a strong proximity resonant enhancement to the power spectrum. At higher frequency, f2, there is some cancellation, and a much weaker power spectrum (second inset). At still higher frequency, f3, many of the peaks again line up with the positive parts of the cosine, resulting in a local maximum in the power. — Eric J. Heller, Why You Hear What You Hear- An…, 1137

Categorization

• CANDY: A neat mental picture: echo timing makes some frequencies add up constructively and others cancel — explains ‘bright’ and ‘dead’ spots in real spaces.