Audiometric Notch
A sharply localised dip in hearing sensitivity at a specific frequency—most characteristically at 4000 Hz—surrounded by better thresholds above and below, classically associated with noise-induced cochlear damage.
Full Definition
An audiometric notch is a pathognomonic pattern on the audiogram characterised by a focal threshold elevation at a discrete frequency, most typically 4000 Hz, with relative recovery at 8000 Hz. This configuration results from the preferential vulnerability of outer hair cells in the basal cochlea to high-intensity noise exposure. The 4000-Hz notch is widely regarded as a hallmark of noise-induced cochlear damage, though similar notches may appear at 3000 or 6000 Hz. Editors should note that 'notch' is the preferred clinical term; 'dip' or 'trough' are colloquial alternatives that should be avoided in formal reports.
Usage
Usage note: Colloquial terms such as 'dip' or 'trough' should be replaced with 'notch' in formal audiological documentation. Always specify the frequency at which the notch occurs.
In Context
- "A classic audiometric notch at 4000 Hz was noted bilaterally, consistent with a history of occupational noise exposure." — Occupational audiological assessment report
- "The audiometric notch deepened by 10 dB over a five-year monitoring period." — Longitudinal hearing surveillance record