Loudness

Loudness is the quality of a sound that is the primary psychological correlate of physical strength (amplitude).

Loudness, a subjective measure, is often confused with objective measures of sound pressure such as decibels or sound intensity. Filters such as A-weighting attempt to adjust sound measurements to correspond to loudness as perceived by the average human. However, as the perception of loudness varies from person to person it cannot be universally measured using any single metric.

Loudness is also affected by parameters other than sound pressure, including frequency and duration.