ITU-R 468 noise weighting

Posted on Feb 7, 2014

ITU-R 468 is a standard relating to noise measurement, widely used when measuring noise in audio systems. The standard defines a weighting filter curve, together with a quasi-peak rectifier having special characteristics as defined by specified tone-burst tests. It is currently maintained by the International Telecommunications Union who took it over from the CCIR. It is used especially in the UK, Europe, and

ITU-R 468 noise weighting
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former countries of the British Empire such as Australia and South Africa. [ citation needed ] It is less well known in the USA where A-weighting has always been used. [ citation needed ] While most audio engineers are familiar with the A-weighting curve, which was based on the 40 phon equal-loudness contour derived initially by Fletcher and Munson (1933) the later CCIR-468 weighting curve, now supported as an ITU standard is less well known outside of the UK and Europe. Originally incorporated into an ANSI standard for sound level meters, A-weighting was intended for measurement of the audibility of sounds by themselves. It was never specifically intended for the measurement of the more random (near- white or pink ) noise in electronic equipment, though has been used for this purpose by most microphone manufacturers since the 1970s. The human ear responds quite differently to clicks and bursts of random noise, and it is this difference that gave rise to the 468-weighting, which together with quasi-peak measurement (rather than the rms measurement used with A-weighting) became widely used by broadcasters throughout Britain, Europe, and former British Commonwealth countries, where engineers were heavily influenced by BBC test methods. Telephone companies worldwide have also used methods similar to 468 weighting with quasi-peak measurement to describe objectionable interference induced in one telephone circuit by switching...

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