Editing Weighting curve

{{Use dmy dates|date=May 2021|cs1-dates=y}}
A '''weighting curve''' is a graph of a set of factors, that are used to 'weight' measured values of a variable according to their importance in relation to some outcome. An important example is [[frequency]] weighting in sound level measurement where a specific set of weighting curves known as [[A-weighting|A-]], [[B-weighting|B-]], [[C-weighting|C-]], and [[D-weighting]] as defined in IEC 61672<ref name="IEC 61672"/> are used. Unweighted measurements of sound pressure do not correspond to perceived loudness because the human ear is less sensitive at low and high frequencies, with the effect more pronounced at lower sound levels. The four curves are applied to the measured sound level, for example by the use of a [[weighting filter]] in a sound level meter, to arrive at readings of loudness in [[phon]]s or in decibels (dB) above the threshold of hearing (see [[A-weighting]]).

==Weighting curves in electronic engineering, audio, and broadcasting==
Although A-weighting with a slow RMS detector, as commonly used in sound level meters<ref name="IEC 61672"/> is frequently used when measuring noise in audio circuits, a different weighting curve, [[ITU-R 468 noise weighting]] uses a psophometric weighting curve and a quasi-peak detector.<ref name="IEC 60268-1"/> This method, formerly known as [[CCIR weighting]], is preferred by the telecommunications industry, broadcasters, and some equipment manufacturers as it reflects more accurately the audibility of pops and short bursts of random noise as opposed to pure tones. [[Psophometric weighting]] is used in [[telephony]] and [[telecommunications]] where narrow-band circuits are common.
Hearing weighting curves are also used for sound in water.<ref name="Southall_2007"/>

==Other applications of weighting==
Acoustics is by no means the only subject which finds use for weighting curves however, and they are widely used in deriving measures of effect for sun exposure, gamma radiation exposure, and many other things. In the measurement of [[gamma rays]] or other [[ionising radiation]], a radiation monitor or [[dosimeter]] will commonly use a filter to attenuate those energy levels or wavelengths that cause the least damage to the human body, while letting through those that do the most damage, so that any source of radiation may be measured in terms of its true danger rather than just its "strength". The [[sievert]] is a unit of weighted radiation dose for [[ionising radiation]], which supersedes the older weighted unit the rem ([[roentgen equivalent man]]).

Weighting is also applied to the measurement of sunlight when assessing the risk of skin damage through [[sunburn]], since different wavelengths have different biological effects. Common examples are the [[sun protection factor|SPF]] of sunscreen, and the [[ultraviolet index]].

Another use of weighting is in television, where the red, green, and blue components of the signal are weighted according to their perceived brightness. This ensures compatibility with black-and-white receivers, and also benefits noise performance and allows separation into meaningful [[luminance (video)|luminance]] and [[chrominance]] signals for transmission.

==See also==
* [[Weight function]]
* [[Weighted arithmetic mean]]
* [[Weighting]]
* [[Weighting filter]]
* [[A-weighting]]
* [[A-weighting#B|B-, C-, D-, G-, and Z-weightings]]
* [[M-weighting]]

==References==
{{Reflist|refs=
<ref name="IEC 61672">IEC 61672, which has superseded IEC 60651, IEC 651, and earlier standards</ref>
<ref name="IEC 60268-1">IEC 60268-1</ref>
<ref name="Southall_2007">{{cite journal |author-last1=Southall |author-first1=B. L. |author-last2=Bowles |author-first2=A. E. |author-last3=Ellison |author-first3=W. T. |author-last4=Finneran |author-first4=J. J. |author-last5=Gentry |author-first5=R. L. |author-last6=Greene |author-first6=C. R. |author-last7=Tyack |author-first7=P. L. |display-authors=etal |date=2007 |title=Overview |journal=Aquatic Mammals |volume=33 |number=4 |pages=411–414|doi=10.1578/AM.33.4.2007.411|bibcode=2007AqMam..33..411S }}</ref>
}}

[[Category:Audio engineering]]
[[Category:Noise]]
[[Category:Sound]]