Audio
What are decibels (dB)?
The decibel (dB) is the unit used to express how intense a sound is. The scale is not linear but logarithmic: every extra 10 dB is perceived as roughly twice as loud. That is why a difference that looks small on a spec sheet can be large to the ear.
How to read the figure
As a general reference: a whisper is around 30 dB, a normal conversation around 60 dB and heavy traffic around 85 dB. These are approximate values, because the figure changes with the distance at which it is measured.
A logarithmic scale has two practical consequences: 3 dB more equals twice the sound energy, and 10 dB more sounds about twice as loud. A 35 dB fan is not "a bit" noisier than a 25 dB one: it sounds roughly twice as loud.
Decibels on product pages
On a device with a motor (a fan, a massager, a purifier) the dB figure is the noise it makes: lower means quieter. On noise cancelling headphones it is how much outside noise they reduce: there, higher is better.
Headphones for children commonly limit volume to 85 dB. That figure is used because prolonged exposure to higher levels can damage hearing; the risk depends on both the volume and how long you listen.
What to check before you buy
- Before comparing, check what the figure measures: noise the device produces or noise it reduces.
- To sleep with a device running, look for the noise level of its lowest mode, not its maximum.
- Compare figures measured under similar conditions: measuring distance changes the result.
Frequently asked questions
Below 30 dB a device is barely noticeable in a calm room. Between 30 and 40 dB it is audible but rarely disturbs sleep. This is general guidance: sensitivity to noise varies from person to person.