Safe Listening Time by dB: NIOSH Chart

Read the table as one model

Each row assumes a steady A-weighted level and the NIOSH occupational reference. It does not combine different activities automatically, and it does not include uncertainty in an instrument. The time is a modelled duration corresponding to the reference dose, not a suggested target to use up. If a chart simply says safe time without identifying its model, averaging method and period, it leaves out information that changes the result. NIOSH recommended-standard criteria.

The arithmetic behind every row

The duration in hours is T = 8 × 2^((85 − L)/3), where L is the A-weighted level used in this model. Increasing L from 85 to 88 makes the exponent decrease by one, so the time halves from eight hours to four. Another increase to 91 halves it again to two hours. The table continues that same arithmetic rather than adding a fixed number of minutes per decibel. These calculated examples do not require inventing a typical level for an activity.

Read fractional minutes carefully: 7.5 minutes means seven minutes and thirty seconds, while 3.75 minutes means three minutes and forty-five seconds. Those conversions help explain the table, but adding seconds of display precision does not improve the uncertainty of the level used to calculate them.

Mixed periods use fractions of the same reference dose

Suppose a hypothetical observation has two hours at 88 dBA. The table pairs that level with four hours, so the period represents half of the model’s reference dose. Adding a separate hour at 91 dBA adds another half, because that row’s reference duration is two hours. The combined example reaches 100 percent in this calculation even though neither period alone used its full reference time. This is educational arithmetic with stated inputs, not an assessment of a real person’s day.

A brief peak is not the input this table expects

A maximum from a slammed door or a firework is not equivalent to a steady level over a known interval. Impulse noise has additional measurement and risk-characterization issues, and ordinary microphones can overload. Do not place an uncertain phone peak into the formula and report how many seconds of that event are safe. The table is most useful for explaining the level-duration relationship, while actual exposure assessment needs suitable measurement and the appropriate method for the sound involved.

Do not combine this daily table with a weekly allowance

Different public-health and occupational systems use different reference periods and assumptions. A weekly personal-audio allowance and this occupational workday table are not competing estimates of one universal limit. Keep the model’s name beside any exported result. NIOSH explains that its recommended limit is not a general environmental-noise recommendation for everyone outside work. That scope matters when a chart is reused for a concert, a child’s bedroom or hours of leisure listening. NIOSH explanation of scope.

Measurement uncertainty matters more at high levels

Because the relationship is exponential, changing an input by a few decibels can change the time comparison substantially. A browser can show a precise decimal while still having an unknown physical offset or a limited microphone response. Calibration against a suitable reference helps anchor a comparison, but does not turn a phone into certified equipment. If you do not know the actual level, label any calculator example hypothetical. A more precise-looking calculated duration does not repair an uncertain input measurement.

Use the result to support lower exposure

The useful takeaway is that increasing level quickly shortens the corresponding reference duration, and that separate noisy periods accumulate. Seek quieter ways to do a task, take appropriate quieter breaks and use relevant professional assessment for work or official evidence. Do not treat a low percentage as a medical assurance or use the table to justify staying in an uncomfortable environment. Keep your level, time, model and uncertainty together whenever you share an example, so the reference table remains an explanation rather than a personalized prescription.

Sources

• NIOSH criteria and formula
• NIOSH explanation of occupational scope

Phone and browser readings are estimates. For formal decisions, use the specified equipment and procedure; see the accuracy notes.

Try the next check

Noise dose calculator can help with this question. See the matching dB Pulse feature.