Editing Weighting filter (section)

=== Audio reproduction and broadcasting equipment ===
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{{Unreferenced section|date=April 2020}}
{{POV section|date=April 2020}}
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Human sensitivity to noise in the region of 6&nbsp;kHz became particularly apparent in the late 1960s with the introduction of [[compact cassette]] recorders and [[Dolby noise reduction system|Dolby-B noise reduction]]. A-weighted noise measurements were found to give misleading results because they did not give sufficient prominence to the 6&nbsp;kHz region where the noise reduction was having greatest effect, and sometimes one piece of equipment would even measure worse than another and yet sound better, because of differing spectral content.

ITU-R 468 noise weighting was therefore developed to more accurately reflect the subjective loudness of all types of noise, as opposed to tones. This curve, which came out of work done by the [[BBC]] Research Department, and was standardised by the [[Comité consultatif international pour la radio|CCIR]] and later adopted by many other standards bodies ([[International Electrotechnical Commission|IEC]], [[British Standards Institution|BSI]]/) and, {{As of|2006|lc=on}}, is maintained by the ITU. Noise measurements using this weighting typically also use a quasi-peak detector law rather than slow averaging. This also helps to quantify the audibility of bursty noise, ticks and pops that might go undetected with a slow rms measurement.

ITU-R 468 noise weighting with quasi-peak detection is widely used in Europe,<ref>{{cite book |last1=d' Escrivan |first1=Julio |title=Music Technology |date=2012 |publisher=Cambridge University Press |isbn=978-1-107-00080-3 |page=16 |url=https://books.google.com/books?id=pBr49Av4KVEC&pg=PA16 |language=en}}</ref> especially in telecommunications, and in broadcasting particularly after it was adopted by the Dolby corporation who realised its superior validity for their purposes. Its advantages over A-weighting seem to be less well appreciated in the US and in consumer electronics, where the use of A-weighting predominates—probably because A-weighting produces a 9 to 12&nbsp;dB "better" specification, see [[specsmanship]].{{Citation needed|date=April 2010}}{{POV statement|date=April 2010}} It is commonly used by broadcasters in Britain, Europe, and former countries of the British Empire such as Australia and South Africa.

Though the noise level of 16-bit audio systems (such as CD players) is commonly quoted (on the basis of calculations that take no account of subjective effect) as −96&nbsp;dB relative to FS (full scale), the best 468-weighted results are in the region of −68&nbsp;dB relative to Alignment Level (commonly defined as 18&nbsp;dB below FS) i.e. −86&nbsp;dB relative to FS.

The use of weighting curves is in no way to be regarded as 'cheating', provided that the proper curve is used. Nothing of relevance is being 'hidden', and even when, for example, hum is present at 50 or 100&nbsp;Hz at a level above the quoted (weighted) noise floor this is of no importance because our ears are very insensitive to low frequencies at low levels, so it will not be heard.  A-weighting is often used to compare and qualify [[Analog-to-digital converter|ADC]]s, for instance, because it more accurately represents the way [[noise shaping]] hides [[dither]] noise in the [[ultrasound|ultrasonic]] range.