ETC displays can misreport reflection levels by about 20 dB versus audibility

Evidence

In contrast, the (c) displays, showing the ETC measurements were telling us that there might be a difference of about 20 dB in the opposite direction; the narrow-band sound is shown to be lower in level. Obviously, this particular form of the measurement is not a good correlate with the audible effect in this test. — Toole, Floyd E, Sound reproduction- the acoustics and…, 676

Categorization

• QUESTION: Worth chasing why the ETC inversion is so large (~20 dB) — is it energy integration band limits or time-windowing resolution?