The just-detectable speaker shift defines the minimum audible angle.

Evidence

Mills (1958) took a somewhat different approach to measuring the ability to localize sounds and measured the just detectable angle between two sounds. This quantity is commonly called the minimum audible angle (MAA) today. Mills placed a speaker at a specific location (e.g., 0° in front or 90° to the side) and measured how far the speaker must be moved (in degrees) before the listener was able to determine that the speaker was in a different location. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 1495

Categorization

• DEFINE: Defines MAA operationally as the threshold angle for detecting a change in speaker location.
• XREF: Establishes the spatial analog of auditory acuity that later chapters will compare in hearing-impaired listeners.