Editing Loudness (section)

{{short description|Subjective perception of sound pressure}}
{{For|the Japanese band|Loudness (band)}}
[[Image:Lindos1.svg|thumb|400px|right|The horizontal axis shows ''[[frequency]]'' in ''[[Hertz]]'']]

In [[acoustics]], '''loudness''' is the [[subjectivity|subjective]] perception of [[sound pressure]]. More formally, it is defined as the "attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud".<ref>American National Standards Institute, "American national psychoacoustical terminology" S3.20, 1973, American Standards Association.</ref> The relation of physical attributes of sound to perceived loudness consists of physical, physiological and psychological components. The study of '''apparent loudness''' is included in the topic of [[psychoacoustics]] and employs methods of [[psychophysics]].

{{anchor|Stevens|Zwicker}}In different industries, loudness may have different meanings and different measurement standards. Some definitions, such as [[ITU-R BS.1770]] refer to the relative loudness of different segments of electronically reproduced sounds, such as for broadcasting and cinema. Others, such as ISO 532A (Stevens loudness, measured in [[sone]]s), ISO 532B ([[Eberhard Zwicker|Zwicker]] loudness), DIN 45631 and ASA/ANSI S3.4, have a more general scope and are often used to characterize loudness of environmental noise. More modern standards, such as Nordtest ACOU112 and ISO/AWI 532-3 (in progress) take into account other components of loudness, such as onset rate, time variation and spectral masking.

Loudness, a subjective measure, is often confused with physical measures of sound strength such as sound pressure, [[sound pressure level]] (in [[decibel]]s), [[sound intensity]] or [[sound power]]. [[Weighting filter]]s such as [[A-weighting]] and [[LKFS]] attempt to compensate measurements to correspond to loudness as perceived by the typical human.