Noise Exposure: Explanation of OSHA and NIOSH Safe‑Exposure Limits and the Importance of Noise Dosimetry

It’s a noisy world, and hearing damage from loud sound affects millions of people. Noise‑induced hearing loss (NIHL) and associated disorders of tinnitus, hyperacusis and diplacusis are all irreversible. This is a tragedy, considering that these often debilitating conditions are preventable. The keys to prevention are in understanding the risks and consistently acting to minimize the risks. NEW EVIDENCE FOR URGENCY NIHL and associated disorders (which, for simplification, will be included in the acronym “NIHL”) are caused by overexposure: listening to sound that’s too loud, for too long. NIHL can occur from a single activity such as an explosion or a loud concert, but it usually occurs gradually over many years. Decades of data have shown that noise‑related shifts in hearing appeared to be temporary, a phenomenon known as temporary threshold shift (TTS). With TTS, hearing thresholds typically recover to pre‑noise exposure levels after a period of auditory quiet. Because of this recovery, many of us assumed that the structure and function of the auditory system was affected only temporarily by noise, returning to normal (or pre‑exposure) levels after a period of quiet. We believed that permanen