Decibel Chart
What 30, 60, 85 and 120 dB sound like, and how long each is safe for in a day.
The scale is logarithmic
A decibel is not a unit of loudness the way a metre is a unit of length. It is a ratio, expressed on a log scale: +10 dB is ten times the sound intensity, and +3 dB is roughly twice the intensity. That is why 100 dB is not "a bit more" than 90 dB — it is ten times the energy, and the safe exposure time drops by a factor of ten.
The ear does not follow the scale exactly: a 10 dB increase is usually heard as "about twice as loud". The two rules — energy and perception — are both worth keeping straight.
Common sounds
| Level | Source | Safe daily exposure |
|---|---|---|
| 10 dB | Breathing, rustling leaves | 8 h+ |
| 30 dB | Whisper, quiet bedroom at night | 8 h+ |
| 40 dB | Library, quiet residential street | 8 h+ |
| 50 dB | Refrigerator, quiet office | 8 h+ |
| 60 dB | Normal conversation, air conditioning | 8 h+ |
| 70 dB | Vacuum cleaner, shower, busy office | 8 h+ |
| 80 dB | Alarm clock, city traffic from inside a car | 8 h+ |
| 85 dB | Heavy traffic, noisy restaurant | 8 h |
| 90 dB | Lawn mower, blender, shouted conversation | 2 h 30 min |
| 95 dB | Motorcycle, food processor | 47 min |
| 100 dB | Subway platform, nightclub, chainsaw at close range | 15 min |
| 105 dB | Rock concert, headphones at high volume | 4 min 43 s |
| 110 dB | Front row at a concert, leaf blower | 1 min 29 s |
| 120 dB | Ambulance siren, thunderclap, jet at 100 m | 8.9 s |
| 130 dB | Jet engine at take-off distance, pain threshold | 0.9 s |
| 140 dB | Gunshot, fireworks at close range | Immediate risk |
The exposure column uses the NIOSH recommended limit: 85 dBA for eight hours, halving for every 3 dB above that. Values are rounded; the exact arithmetic is 28,800 seconds divided by 2(dB−85)/3.
Why 85 dB is the reference
85 dBA for eight hours is the level at which most national regulators require hearing protection and monitoring in workplaces. The 3 dB exchange rate reflects how the ear accumulates damage: energy doubles with every 3 dB, so the exposure time must halve to keep the total dose constant.
Some regulators use a 5 dB exchange rate instead, which allows longer exposures at high levels. The difference is not academic: at 100 dB, a 5 dB rule permits about an hour where the 3 dB rule permits 15 minutes.
Distance changes everything
- Point source in open air: roughly −6 dB per doubling of distance. A machine at 100 dB at 1 m is about 94 dB at 2 m and 88 dB at 4 m.
- Line source such as a motorway: about −3 dB per doubling.
- Indoors, reflections matter. A hard room can keep the level nearly constant as you move away; soft furnishings absorb it.
dBA, dBC and "dB"
A flat decibel reading counts low frequencies as heavily as mid frequencies. The A-weighting curve discounts low frequencies to match human hearing, which is why noise regulations are written in dBA. A bass-heavy engine can read 95 dB flat but 80 dBA.
Browser meters do not apply A-weighting, so their raw readings sit somewhere between dB and dBC. This is another reason the number is an estimate, not a compliance measurement.
Signs that the level is too high. You have to raise your voice to be heard at arm's length, your ears ring afterwards, or sounds feel muffled the next morning. Those are reasons to move away or use hearing protection, whatever a meter says.
Questions
Can one loud concert damage hearing permanently?
It can. Permanent damage depends on level, duration and individual susceptibility, and a single very loud event can cause a permanent threshold shift. Ringing that lasts more than a few minutes is a warning sign worth taking seriously.
Is 85 dB dangerous?
Not for eight hours, by the standard. It becomes a problem when it is the background of a whole working day, because the dose is cumulative and the limit assumes no other exposure. Two hours at 88 dB plus six at 85 dB is already over the daily dose.
Do headphones count toward the daily dose?
Yes. The level at your eardrum is what matters, not the source. Headphones at 100 dB for 15 minutes use the same daily allowance as a subway platform.
Why do two phones disagree by 10 dB?
Different microphones, different gain calibration and different processing. Without a reference meter there is no way to know which is closer; the offset control exists for exactly this reason.