SoundSense

Safe noise levels: how long is safe at each decibel level

Sound at or below 70 dBA is unlikely to damage your hearing, even over long periods. From 85 dBA, long or repeated exposure can cause permanent hearing loss, and the safe time falls quickly as the level rises: by the NIOSH rule, every 3 dB louder halves it. At 85 dBA the limit is 8 hours a day; at 100 dBA it is 15 minutes.

The figures below come from the US National Institute for Occupational Safety and Health (NIOSH), the World Health Organization (WHO), the US workplace regulator OSHA and the EU noise-at-work directive. Each answers a slightly different question, which is why their numbers differ.

Safe time per day: the NIOSH limits

NIOSH recommends a limit of 85 dBA averaged over an 8-hour working day. It uses a 3 dB exchange rate: each 3 dB increase halves the time you can spend at that level.

Average level Safe time per day
85 dBA 8 hours
88 dBA 4 hours
91 dBA 2 hours
94 dBA 1 hour
97 dBA 30 minutes
100 dBA 15 minutes

This is the most widely used protective limit, and it works for everyday life as well as work: a two-hour concert at an average of 100 dBA is eight times the daily dose.

Safe time per week: the WHO safe listening table

The WHO gives a weekly allowance, made for music, events and other noise you choose to be around.

Level WHO example Safe time per week
60 dB and below Normal conversation No limit
80 dB Doorbell 40 hours
85 dB Heavy traffic, heard inside a car 12 hours 30 minutes
90 dB Shouted conversation 4 hours
95 dB Motorcycle 1 hour 15 minutes
100 dB Hair dryer 20 minutes
105 dB Car horn at 5 metres 8 minutes
110 dB Shouting in the ear 2.5 minutes
120 dB Standing near a siren 12 seconds
130 dB Jackhammer Under 1 second
140 dB Aeroplane taking off None

Workplace limits in the US and the EU

These are legal rules for employers, not health targets for the rest of the day.

Rule What it sets
OSHA (US), 29 CFR 1910.95 90 dBA for 8 hours, 95 dBA for 4 hours, 100 dBA for 2 hours, 105 dBA for 1 hour, 115 dBA for 15 minutes or less. From an 85 dBA average over 8 hours, employers must run a hearing conservation programme.
EU Directive 2003/10/EC Action at 80 dB(A) (hearing protection made available) and at 85 dB(A) (hearing protection must be worn); exposure must never exceed 87 dB(A), counted with the hearing protection the worker wears.

OSHA's limit is less protective than NIOSH's because it uses a 5 dB exchange rate: it allows 2 hours at 100 dBA, where NIOSH allows 15 minutes. If you are deciding what is safe for yourself, use the NIOSH table. The full OSHA table and what employers must do from 85 dBA are on OSHA noise limits.

What a decibel is, and why small changes matter

Decibels are logarithmic. A sound 10 dB louder carries ten times the sound energy, and 3 dB louder carries twice the energy. That is why 88 dBA for 4 hours gives the same dose as 85 dBA for 8 hours.

The "A" in dBA means the reading is A-weighted: it counts frequencies the way the human ear hears them, giving less weight to very low and very high sounds. Health limits are written in dBA, so that is the number to look at.

How to check the noise around you

Exposure limits are about the average level over time, not the loudest moment. To see where a place stands:

  1. Measure for a few minutes, not a few seconds, where you actually spend the time: your desk, your seat at the venue, your bedroom.
  2. Read the average (LAeq) and compare it with the tables above. The maximum tells you about peaks, not about dose.
  3. Note how long you are there. Two hours at 94 dBA is already twice the NIOSH daily limit.

SoundSense shows the average (LAeq), minimum and maximum for each saved check, and how long the level stayed above a threshold you choose, so you can set it to 85 dBA and see the time above it. Phone readings are estimates; for a workplace assessment, use a certified sound level meter or a noise dosimeter.

Sources

Updated by the SoundSense team at Just IT.