Loudness

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This article is about sound loudness. For the Japanese band "Loudness", see Loudness (band).

The horizontal axis shows frequency in Hz

Loudness is the quality of a sound that is the primary psychological correlate of physical intensity. Loudness, a subjective measure, is often confused with objective measures of sound intensity such as decibels. Filters such as A-weighting attempt to adjust intensity measurements to correspond to loudness as perceived by the average human. However, true perceived loudness varies from person to person and cannot be measured this way.

Loudness is also affected by parameters other than intensity, including: frequency (see bandwidth), and duration (see temporal integration).

1 Explanation
2 Loudness and hearing loss
3 Other uses of the word loudness
4 See also

[edit] Explanation

Loudness is often approximated by a power function with an exponent of 0.6 when plotted vs. sound pressure or 0.3 when plotted vs. sound intensity (Stevens' power law). More precise measures have been subsequently made that show that loudness grows more rapidly (with a higher exponent) at low and high levels and less rapidly (with a lower exponent) at moderate levels. Units used to measure loudness:

Sone (loudness N)
Phon (loudness level L)

[edit] Loudness and hearing loss

When sensorineural hearing loss (damage to the cochlea) is present, the perception of loudness is altered. Sounds at low levels (often perceived by those without hearing loss as relatively quiet) are no longer audible to the hearing impaired, but interestingly, sounds at high levels often are perceived as having the same loudness as they would for an unimpaired listener. A common cause of sensorineural hearing loss is exposure to elevated sound levels.