Noise-Induced Hearing Loss (NIHL)

Noise-induced hearing loss is permanent sensorineural hearing loss caused by damage to the cochlea's hair cells from excessive sound levels. It is one of the most preventable forms of hearing loss. NIHL can result from a single extremely loud event (acoustic trauma, such as an explosion) or from repeated exposure to moderate to high sound levels over time.

Sounds above 85 decibels can cause cumulative cochlear damage with prolonged exposure. Common sources of harmful noise include heavy machinery, construction equipment, firearms, and sustained loud music. NIHL typically affects high-frequency hearing first, particularly around 4,000 Hz, a pattern seen on the audiogram as a characteristic notch. The damage is irreversible.

In Canada, the Canadian Centre for Occupational Health and Safety (CCOHS) sets guidelines for workplace noise exposure limits and recommends hearing conservation programs for workers in high-noise environments. Hearing protection is the primary prevention strategy.