Sound waves form standing patterns only when wavelength relates to reflector spacing

Evidence

At most frequencies, the distance between the two boundaries will not be related to the wavelength, and so the compression and rarefaction peaks and troughs will occupy all positions between the two boundaries with equal probability, as shown in Figure 1.31. However, when the wavelength is related to the distance between the two boundaries, the wave keeps tracing the same path as it travels between the two boundaries. This means that the compressions and rarefactions always end up in the same position between the boundaries. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 387

Categorization

• DEFINE: Clarifies the precise condition under which a traveling wave becomes a resonant standing pattern, which is the core of the standing-wave definition.
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 387