figure 5.35 The decibel scale The measuring unit that scientists use to measure the physical intensity of sound waves is decibels (dB). On a decibel scale, a sound of 10 dB is 10 times louder than one of 0 dB; a 20-dB sound has 10 times the intensity of a 10-dB sound; and so forth. Zero decibels is the physical intensity required for the experience of hearing.