Standing waves form when wavelengths match room dimensions

Evidence

Sounds of all frequencies and wavelengths reflect around rooms in a somewhat chaotic manner, but when the wavelengths are of the same order as the dimensions of a room, some special events occur. Between parallel surfaces that are half a wavelength apart, or multiples of half-wavelengths apart, the sound traveling in both directions add constructively, reinforcing each other, and a standing wave develops. This is the basis of a room mode or resonance. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1018

Categorization

• DEFINE: Precise definition of the mechanism behind room modes and standing waves.