How loud is 40 decibels?
40 dB is quiet: a library, a calm suburb at night, a fridge humming in the next room. Most people find this level relaxing and easy to concentrate in.
- Sounds like
- A quiet library
- Loudness
- Quiet to moderate
- Safe per day (NIOSH)
- No limit
- OSHA workplace limit
- Below the limit
40 dB on the decibel scale
Tap another sound to compare- Safe · under 65 dB
- Caution · 65–85 dB
- Risk · over 85 dB
What 40 dB sounds like
- A library
- A quiet residential street at night
- A quiet office with no one talking
- Soft background hum of a fridge
Good classrooms and private offices aim for 35–40 dB of background noise so that speech stays clear without anyone raising their voice.
Is 40 dB safe?
Yes. 40 dB is well below the level where hearing damage starts, so you can be around it all day. This is a level most people find restful.
40 dB compared with other sounds
| Compared with | Difference | Sounds | Sound energy |
|---|---|---|---|
| Whisper (30 dB) | +10 dB | 2× as loud | 10× more |
| Conversation (60 dB) | −20 dB | 4× quieter | 100× less |
| Heavy traffic (85 dB) | −45 dB | 23× quieter | 31,623× less |
| Concert (110 dB) | −70 dB | 128× quieter | 10,000,000× less |
Rule of thumb: +10 dB sounds about twice as loud and carries ten times the energy. See what is a decibel.
How to check if a sound is 40 dB
Open the free online decibel meter on this site and allow the microphone. Hold your phone or laptop where your ears would be, wait a few seconds, and read the average rather than the momentary number. For a reliable, calibrated reading you can save or show to someone else, use the Decibel Meter app on iPhone.