Industry-related terminology defined.
Audiogram: A graph or table which records an individual’s hearing threshold levels across various test frequencies. Hearing thresholds are displayed in decibels (dB) and test frequencies in hertz (Hz).
Audiometer: The electronic instrument used to obtain hearing threshold levels across various test frequencies.
CAOHC: The Council for Accreditation in Occupational Hearing Conservation. The Council accredits hearing conservation training courses, certifies audiometric technicians, and provides education, information, and guidance to all industries regarding the implementation of occupational hearing conservation programs.
Decibel (dB): Named after Alexander Graham Bell, the unit is used to express the intensity of sound. The decibel scale is a logarithmic scale in which 0 dB at any test frequency on an audiogram approximates the hearing threshold level of healthy young adults.
dBA: Sound filtered through the A-weighted network of a sound level meter. A-weighting excludes some low and very high-frequency sounds, similar to the way the human ear perceives sound of medium intensity. Noise measurement in the workplace often uses A-weighting because of its similarity to human hearing, as well as to assess damage risk to hearing sensitivity.
OHC: Occupational hearing conservationist certified by CAOHC.
STS: Standard threshold shift, defined as a change in hearing threshold relative to the baseline audiogram of an average of 10 dB or more at 2000, 3000, 4000 Hz in either ear.
TWA: Time-weighted average; expressed in dBA, a single-number average of varying noise exposures usually over an 8-hour period. For example, OSHA requires provision of annual hearing testing and hearing conservation training when an employee’s 8-hour TWA reaches a level of 85 dBA or greater (85 for 8 hours, 90 for 4 hours, 95 for 2 hours, etc.).