If you've ever rocked out at a loud concert and woken up the next day with noticeably muffled hearing, you may have wondered: Did I just damage my ears? The answer to that is complex. As far as the muffled hearing, what you experienced is called temporary threshold shift. This happens when the tiny hairs of your inner ear, the ones that sense sound pressure waves, become fatigued. Research into the relationship between temporary threshold shift, which doesn't last, and permanent threshold shift, which does, is ongoing, and scientists aren't sure whether one causes the other or they have separate causes. One thing is for sure: exposing yourself to very loud noise, like that of a rock concert, dance club, or cranked-up headphones, can cause permanent hearing loss.
To know whether the noise you're hearing is loud enough to be harmful, it's good to have a basic understanding of decibels. Decibels are units of sound pressure level, and the louder the sound, the higher the decibels. For example, a soft whisper is around 35 decibels, a vacuum cleaner is around 75 decibels, and a dance club is usually about 110 decibels. You can measure decibels yourself with a variety of smartphone apps. To know how loud is too loud, just look to the Occupational Safety and Health Administration (OSHA), which provides guidelines for how much noise is safe for U.S. workers to be exposed to before they experience an unacceptable risk of hearing damage. In an eight-hour day, OSHA sets a limit of 85 decibels, then cuts the acceptable time by half for every 5 decibels. This means that if work noise were to match the 110 decibels of a dance club, OSHA regulations wouldn't permit that worker to stay there for any longer than 30 minutes. Learn more about hearing damage and how to protect yourself with the videos below.