Audiometric Testing
Audiometric testing is a calibrated hearing test that measures auditory thresholds across frequencies to establish a baseline and detect noise-induced hearing loss over time. In manufacturing, it is part of hearing conservation programs for workers exposed to noise at or above 85 dBA TWA. The test is performed in a sound-treated booth using a calibrated audiometer; results are plotted on an audiogram for comparison of hearing sensitivity over time.
In a CNC machining context, audiometric testing is part of a hearing conservation program for operators exposed to noise at or above 85 dBA TWA. Continuous noise from spindles, chip evacuation, vacuum systems, saws, compressors, and tool chatter can push operators into the hazardous exposure range. The test is performed in a sound-treated booth by an audiologist or certified tester after 16 hours of quiet to avoid temporary threshold shifts. Baseline and annual audiograms detect early hearing changes before permanent loss. Process changes like heavier cuts, dull tooling, or chatter can raise exposure, so audiometry is paired with noise surveys. It is a surveillance tool, not a performance test, and does not replace fixing root causes like worn bearings or air leaks.
What does an audiogram show?
It records hearing threshold levels by frequency across standard test tones; comparison between baseline and later tests shows whether hearing sensitivity is changing over time.
What exposure level typically triggers testing?
A common trigger is 85 dBA over 8 hours (TWA), although exact legal duties depend on jurisdiction and whether hearing protectors are used as a control measure.
Why does a CNC shop care about this if the machines are 'normal'?
Even routine production noise can accumulate into hazardous exposure. Machining studies show that acoustic emissions and process noise are strong enough to support real-time monitoring of tool conditions and abnormal cutting events, so hearing conservation becomes part of broader shop-floor risk control.