A logarithmic measurement unit that describes a sound’s relative loudness, though it can also be used to describe the relative difference between two power levels. A decibel is one tenth of a Bel. In sound, decibels generally measure a scale from 0 (the threshold of hearing) to 130 dB (the threshold of pain). A 3dB difference equates to a doubling of power whereas a 6dB difference corresponds to a doubling in sound pressure level. A 1dB difference over a broad frequency range is noticeable to most people, while a 0.5dB difference can affect the subjective impression of a sound.