Sound measure is a term used to describe the measurement of sound. The most common units of sound measure are decibel (dB), sone, BEL, and phon. Decibel is a unit of sound intensity, which is measured in logarithmic scale. Sone is a unit of loudness, which is based on the subjective perception of sound. BEL is a unit of sound power, which is equal to 10 decibels. Phon is a unit of loudness, which is based on the average hearing threshold of humans.