Room standing waves mask the adjacent-boundary effect even after averaging.

Evidence

It was done multiple times in different locations around the room, and the results averaged—individual curves were heavily influenced by standing waves and were variable. However, there is evidence of the microphone being near the null in the first-order vertical room mode at 62 Hz because this was common to all measurements. Otherwise, the untidy averaged curves may be impossible to interpret, but it is clear that there are gains in sound level for each halving of the solid angle. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1460

Categorization

• XREF: This mirrors the ‘grafting and growth’ methodological tidiness — clean field measurements vs. messy in-room reality — and the challenge of isolating single mechanisms inside a complex system.