Safe Decibel Levels for Humans: What Federal Noise Rules Set

OSHA's Table G-16, as printed

The most quoted noise chart in the United States is a table in a workplace rule. OSHA's occupational noise standard, 29 CFR 1910.95, prints Table G-16, "Permissible Noise Exposures," in nine rows. It starts at 8 hours a day at 90 dBA and ends at a quarter hour or less at 115 dBA; the table above copies every row as printed, fractions included.

Three things in the rule shape how the table is read:

• How the level is measured. The levels are read on the A scale of a standard sound level meter at slow response, which is why they're written in dBA.
• Mixed days. A footnote says that when a day has periods at different levels, their combined effect counts, not the effect of each period on its own. A shift with some time at 95 dBA and some at 100 dBA isn't judged row by row.
• Sudden noise. For impulsive or impact noise, the rule sets a separate line: it should not exceed 140 dB peak sound pressure level.

The table binds employers in general industry. It doesn't describe what is safe for your ears at a concert, with headphones or at home, and we don't work out an allowed time for any level that falls between two rows.

OSHA's 85 dBA line: hearing conservation and free protectors

A lower level matters as much as the table. Under 29 CFR 1910.95(c), an employer must run a continuing hearing conservation program whenever workers' noise exposure equals or exceeds an 8-hour time-weighted average of 85 decibels on the A scale, at slow response.

The same rule says employers must make hearing protectors available to every employee exposed at an 8-hour average of 85 decibels or more, at no cost to the employee, and replace them as necessary. So the worker doesn't pay for earplugs or earmuffs at that exposure. Our earplugs page explains how those protectors are rated.

NIOSH's recommended limit: 85 dBA and a 3 dB exchange rate

NIOSH publishes a recommendation rather than a rule. Its recommended exposure limit (REL) for occupational noise is 85 A-weighted decibels over an eight-hour shift, and NIOSH writes that noise above 85 dBA "is considered hazardous."

NIOSH also states how it measures. Its recommended sound level meter settings use A-weighting, slow response and an exchange rate of 3 dB. MSHA's rule defines an exchange rate as the increase in level that halves the allowed exposure time. In NIOSH's terms, a noise dose of 100% or more means a worker has gone past the daily limit.

The REL is the figure NIOSH recommends to employers. OSHA and MSHA enforce their own levels, listed in the table above, and a recommendation from NIOSH doesn't change what an employer is legally required to do.

Mines: MSHA's action level, PEL and dual protection

Mines have their own noise rule. The Mine Safety and Health Administration writes its own in 30 CFR Part 62, with levels measured as an 8-hour time-weighted average:

• Action level, 85 dBA. At or above it, the mine operator must enroll the miner in a hearing conservation program.
• Permissible exposure level, 90 dBA. Above it, the operator must use all feasible engineering and administrative controls to bring the exposure down.
• Dual hearing protection level, 105 dBA. Above it, the operator must provide and ensure the use of an ear plug and an ear muff at the same time.
• A ceiling of 115 dBA. No miner may be exposed above it at any time, measured without counting any hearing protector.

The rule states its exchange rate outright: 5 decibels. NIOSH's recommended meter settings use 3 dB, so the two don't count time the same way above their limits.

The EPA label on hearing protectors

Earplugs and earmuffs sold in the United States carry a label set by the Environmental Protection Agency in 40 CFR Part 211. Its primary label has fixed areas: Area A must state "Noise Reduction Rating," and Area B the Noise Reduction Rating (NRR) in decibels for that model. Area C must say that the range of ratings for existing hearing protectors is approximately 0 to 30, with higher numbers denoting greater effectiveness.

The number comes from a laboratory test: the rule refers to ANSI Std S3.19-1974 tests. A label tells you how a model scored in that test, not how loud the world will be with it in. Our earplugs page covers what the NRR leaves out, by use.