Hearing protection is required in any workplace where noise levels reach or exceed 85 decibels averaged over an eight-hour shift, and it becomes legally mandatory under federal OSHA standards at 90 decibels over the same period. Outside of work, the same thresholds apply to your ears: any repeated exposure above 85 dB, whether from power tools, concerts, or motorsports, can cause permanent hearing loss over time.
OSHA’s Legal Requirements
OSHA sets enforceable limits on how long workers can be exposed to noise at specific levels. The permissible exposure limit (PEL) is 90 dBA over an eight-hour workday. As noise gets louder, the allowable time drops sharply:
- 90 dB: 8 hours
- 95 dB: 4 hours
- 100 dB: 2 hours
- 105 dB: 1 hour
- 110 dB: 30 minutes
- 115 dB: 15 minutes or less
When noise exceeds these limits, employers must provide hearing protection and ensure workers use it. Sudden, explosive sounds (impact or impulse noise) must never exceed 140 dB peak sound pressure, regardless of duration. A single exposure at that level can cause immediate, permanent damage.
OSHA also requires employers to implement a hearing conservation program when the eight-hour average hits 85 dB. That program includes regular hearing tests, noise monitoring, and making hearing protection available to workers, even though the legal ceiling for mandatory use is 90 dB.
NIOSH’s Stricter Recommendation
The National Institute for Occupational Safety and Health (NIOSH) recommends a lower threshold: 85 dBA over an eight-hour shift. NIOSH also uses a more protective calculation method. For every 3 dB increase in noise, the safe exposure time is cut in half. That means 88 dB is safe for only 4 hours, 91 dB for 2 hours, and 100 dB for just 15 minutes.
OSHA’s formula is more lenient, halving the time every 5 dB instead of every 3. The practical difference is significant. At 100 dB, OSHA allows 2 hours of unprotected exposure while NIOSH says you should limit it to 15 minutes. Most hearing health experts consider the NIOSH guidelines closer to the biological reality of how noise damages the inner ear.
Noise Levels in Common Activities
You don’t need to work on a construction site to encounter hazardous noise. A gas-powered lawn mower produces about 107 dB. A chain saw at three feet hits roughly 110 dB. A pneumatic chipper at ear level reaches 120 dB. At that level, damage can begin in as little as 9 seconds of repeated exposure.
Quieter sources can still be a problem if exposure is long enough. A school cafeteria or busy restaurant can hover around 85 dB. That’s the threshold where prolonged, repeated exposure over months or years starts to cause measurable hearing loss. If you regularly spend hours in environments at or above that level, whether at work, in a workshop, or at live music venues, hearing protection is a smart choice even when it’s not legally required.
How Noise Damages Hearing
Noise-induced hearing loss happens in two ways. Repeated exposure to sounds at or above 85 dB gradually destroys the tiny hair cells in the inner ear that convert sound waves into nerve signals. Those cells do not regenerate. The damage accumulates over years, which is why many people don’t notice the loss until it’s significant. A one-time blast at or above 120 dB can cause immediate, permanent damage without any prior exposure history. At 140 dB, a single impulse can rupture the eardrum or destroy inner ear structures instantly.
Types of Hearing Protection
The three main categories are earplugs, earmuffs, and canal caps. Each fits different situations, and picking the right one depends on the noise level, the work environment, and how long you’ll be wearing them.
Earplugs slide into the ear canal. Foam versions are rolled and inserted, then expand to seal the canal. Pre-formed plugs come ready-shaped, and custom-molded plugs are made from an impression of your ear. Earplugs tend to be the most comfortable option for long wear and hot environments. Foam plugs are cheap and effective but not ideal if you’re putting them in and taking them out repeatedly, especially with dirty hands.
Earmuffs cover the entire outer ear and are held in place by a headband or clipped to a hardhat. They’re easy to put on and take off, which makes them better for intermittent noise. The downsides: they’re heavier, they trap heat, and the cushion seal can break down in very cold weather. They can also interfere with hardhats, helmets, respirators, or safety glasses.
Canal caps sit over the ear canal opening and are held by a lightweight band. They’re a middle ground, easier to pop on and off than earplugs but less bulky than muffs. They provide less noise reduction than either of the other options.
Specialty options exist for specific needs. Flat-attenuation earplugs (sometimes called musicians’ plugs) reduce all frequencies evenly, preserving sound quality while lowering volume. Level-dependent protectors let normal conversation pass through but block sudden loud sounds, which is useful for shooting ranges or environments with intermittent noise spikes. Communication headsets with built-in microphones and speakers help workers talk to each other in very loud settings without removing their protection.
How to Read a Noise Reduction Rating
Every hearing protector sold in the U.S. carries a Noise Reduction Rating (NRR) on its label, listed in decibels. This number tells you how much noise the device can theoretically block, but the real-world reduction is lower. When you’re working with typical sound level measurements (A-weighted readings, which most consumer and workplace meters use), subtract 7 from the NRR, then subtract that result from the noise level.
For example, if you’re using earplugs with an NRR of 29 in a 100 dB environment: 29 minus 7 equals 22, and 100 minus 22 equals 78 dB reaching your ear. That puts you well below the 85 dB hazard threshold. If a single protector doesn’t bring the level low enough, wearing earplugs under earmuffs adds further reduction, though it doesn’t simply add the two NRR values together.
A Quick Rule of Thumb
If you have to raise your voice to be heard by someone three feet away, the noise around you is likely at or above 85 dB. That’s your signal to put in hearing protection. At work, your employer is responsible for measuring noise and providing the right equipment. Outside of work, the responsibility falls on you, but the physics of hearing damage don’t change just because you’re mowing your own lawn instead of someone else’s.