The scale is logarithmic, and doubling the intensity of a sound source results in a 3 dB increase in sound. The logarithmic scale is useful for discussing sound because of the ear’s extraordinary sensitivity: The ratio between the loudest sound we can hear without causing permanent damage and the softest sound we can detect is a million to one, when measured as sound-pressure levels in the air; on the dB scale this is 120 dB.
