Glossary definition of 'ITU-R 468 weighting'

(originally CCIR 468) A weighting curve used for measuring noise in audio systems. Whereas A-weighting is based on human response to pure tones at low levels, ITU-R 468 was developed in conjunction with Q-peak response to give results that correlate with human response to noise. It was originally intended for use in assessing FM radio and analogue cassette noise etc.

ITU-R 468 weighting filter

In the screen shot above, the top curve is the ITU-R 468 weighting filter, with 0dB gain at 1kHz. The lower curve, some 5.6dB lower is known as the CCIR/ARM or ITU-R 468 2k weighting and is not actually an ITU-R standard, but was proposed by Dolby Laboratories. The ITU-R 468 curve has 0dB gain at 1kHz, whereas the CCIR/ARM filter is normalized at 2kHz. Apart from the normalization difference of the two curves, the ITU-R 468 weighting is designed to be used in conjunction with a Q-peak response whereas the ARM filter uses an Average-Response Meter (ARM).