A single critical frequency marks the modal to diffuse transition

Evidence

The transition boundary between the region of modal behavior and the region of diffuse behavior is known as the “critical frequency.” As is usual in these situations, although the critical frequency is a single frequency, it is not a sharp boundary: it represents some defined point in a transition region between the two regions. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2025

Categorization

• DEFINE: Defines the critical frequency and clarifies that it designates a transition zone, not a sharp cutoff.
• XREF: connects to: Modal behavior makes diffuse-field analysis fail in a mid frequency range — David Howard, Jamie Angus, coustics and Psychoacoustics, 2073; A defined frequency marks the transition between modal and diffuse acoustic behavior — David Howard, Jamie Angus, coustics and Psychoacoustics, 2078