Loudness of sound is measured in units called ‘decibels’, the measure for everything we hear, including the volume of back up beepers. But why do we use decibels as a unit of measurement? What is the significance of decibels to how humans interpret sound? And how is sound making the world a safer place? We try and answer some of these questions in the article below.

Measuring Sound

As the human ear detects sound on such an enormous dynamic range, it is more convenient to measure sound levels on a logarithmic scale, measured in units called decibels (dB).

Thresholds of sound

The ‘threshold of audibility’ is defined as 0dB, which is essentially when the human ear can start to detect sound. 0 decibels do not mean there is no sound, just that it cannot be heard by the human ear. The ‘threshold of pain’ on the other hand is around 130dB.

How loud is a reversing alarm?

On this scale, daytime background (ambient) noise in the countryside is about 45dB(A) and the background noise in a busy high street is about 65dB(A). A pneumatic ‘jack-hammer’ generates around 100/110dB(A) at 1m.