insertion gain
The difference in sound pressure level at the eardrum with a hearing aid in place compared to without it, measured at a specific frequency.
Full Definition
Insertion gain is the decibel difference between the sound pressure level (SPL) measured at or near the tympanic membrane with a hearing aid fitted versus the SPL in the unaided open ear canal, at a given frequency. It is the primary metric used in real ear measurement (REM) to verify that a hearing aid is providing the prescribed amount of amplification. Insertion gain differs from coupler gain, which is measured in a standardised 2-cc acoustic coupler rather than in the individual's ear. Editors should not use 'insertion gain' and 'functional gain' interchangeably, as functional gain is a behavioural measure. The term should always appear as two words (not 'insertiongain').
Usage
Usage note: Distinguish from functional gain (behavioural, sound-field measure) and from coupler gain (2-cc coupler measure). 'Real ear insertion gain' (REIG) is the more precise technical term used in verification contexts.
In Context
- "Real ear measurement confirmed that insertion gain at 2000 Hz matched the NAL-NL2 target within 5 dB." — Hearing aid verification report
- "The author incorrectly used 'functional gain' where 'insertion gain' was clearly meant, given the probe-microphone measurement context." — Copy-editing query