Sound intensity measurement is a term used to describe the process of measuring the intensity of sound waves. The most common unit of measurement for sound intensity is the decibel (dB), which is a logarithmic unit that measures the ratio of sound pressure level relative to a reference level. Decibels are used to measure the loudness of sound, and can range from 0 dB (the threshold of hearing) to 140 dB (the threshold of pain).