Threshold Shift
A measurable change in a person's hearing threshold level compared to a previous baseline audiogram, indicating a worsening or, less commonly, an improvement in hearing sensitivity.
Full Definition
A threshold shift is the difference in decibels between a current audiometric threshold and a prior reference measurement. A temporary threshold shift (TTS) resolves within hours of noise exposure, whereas a permanent threshold shift (PTS) represents irreversible cochlear damage. In occupational audiology, regulatory frameworks such as OSHA in the United States mandate reporting of standard threshold shifts (STS), defined as an average change of ≥10 dB at 2000, 3000, and 4000 Hz. Editors must distinguish TTS, PTS, and STS as each carries specific clinical and regulatory implications. 'Threshold shift' alone is ambiguous without qualification and should be specified in clinical and legal documents.
Usage
Usage note: Always qualify threshold shift as temporary (TTS), permanent (PTS), or standard (STS) in regulatory and clinical documents; unqualified use is ambiguous.
In Context
- "Serial audiograms demonstrated a progressive threshold shift at 4000 Hz bilaterally over the five-year monitoring period." — Occupational health audiometric surveillance report
- "The report referred to a 'threshold shift' without specifying whether it was temporary or permanent; this must be clarified before submission." — Editorial review of occupational audiology document