Full definition
Unwanted sound capable of causing permanent noise-induced hearing loss (NIHL). Legal limit: 85 dBA for an 8-hour shift (NOM-011-STPS). Each 3 dB increase halves the permissible exposure time (doubling rule). Control hierarchy: reduce at source (isolate, modify machinery), in the path (acoustic barriers, enclosures), or at the receiver (hearing protection). Periodic audiometric testing required for exposed workers.