How is sound measured?
The 'volume' or intensity of sound is measured using the decibel (dB) scale, where 0dB represents the quietest sound that a healthy human ear can hear.
From there, every increase of 3dB means that the sound intensity is doubled. So a sound of 88dB is twice as intense as a sound of 85dB, even though it won't sound twice as loud.
What decibel level is dangerous?
Sounds under 85dB are safe to listen to – you don't need to use any hearing protection. But if you work in a noisy environment and the sound levels reach 80dB, your employer should assess the risk to your hearing and give you information about this.
85dB is the level at which your hearing can become damaged over time. The length of time you can 'safely' be exposed to sound over 85dB without needing to use hearing protection depends on how loud it is.
The safe exposure time for 85dB is eight hours. As sound intensity doubles with every increase of 3dB, the safe exposure time halves. So, for example, the safe exposure time for 88dB is four hours (see guide below).
For sounds of 110-120dB, even a very short exposure time can cause hearing damage.