Utilizamos esta escala para medir a intensidade do son, distinguir se é feble ou forte. Trátase dunha escala logarítmica, na que un aumento de dez unidades quere dicir que o son é 100 veces máis forte. A fórmula da sonoridade relaciona a intensidade do son en cuestión frente a intensidade mímima de audición que é 10^-12 W/m².

dB = 10log I/10^-12

As unidade da sonoridade son os decibelios.

Na seguinte táboa vemos a sonoridade de diversas situacións:

100 dB é o limiar de sensación de dor.

On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful is 20 dB. Here are some common sounds and their decibel ratings:

You know from your own experience that distance affects the intensity of sound. If you are far away the power is greatly diminished. All of the ratings above are taken while standing near the sound.

Any sound above 85 dB can cause hearing loss, and the loss is related to both the power of the sound as well as the lenght of exposure. You know that you are listening to an 85 dB sound if you have to raise your voice to be heard by somebody else. Eigt hours of 90 dB sound can damage your ears; any exposure to 140 dB sound causes inmediate damage ( and causes actual pain).