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.
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).