Rayleigh attributed a forest echo’s octave rise to size-dependent scattering of high frequencies

Evidence

When he heard the echo return an octave up, Rayleigh was carrying his draft manuscript showing that Rayleigh scattering works for sound too, in analogy to his discoveries with light. It was natural for him to propose this as the reason for the octave shift of the woman’s voice. He suggested that branches and leaves, much smaller in diameter than a wavelength of the sound coming from the woman (he didn’t give the frequency, but at 500 Hz it would be just under a meter), preferentially scattered back the short-wavelength, high frequencies of the woman’s voice, causing the octave shift higher. — Eric J. Heller, Why You Hear What You Hear- An…, 2639

Categorization

• DEFINE: Explains Rayleigh scattering’s application to sound and the octave-shift hypothesis.
• XREF: Connects to the reader’s optics background — Rayleigh scattering is classically a light phenomenon, here ported to acoustics. — connects to: Trunk scatter cannot alone explain forest high-frequency sound attenuation — Margaret A. Price, Keith Attenborough, and Nicholas W. Heap, Sound Attenuation through Trees:…, 87