ITU-R 468 noise weighting

ITU-R 468 (originally defined in CCIR recommendation 468-4, therefore formerly also known as CCIR weighting; sometimes referred to as CCIR-1k) is a standard relating to noise measurement, widely used when measuring noise in audio systems. The standard, now referred to as ITU-R BS.468-4, defines a weighting filter curve, together with a quasi-peakrectifier having special characteristics as defined by specified tests. It is currently maintained by the International Telecommunication Union who took it over from the CCIR.

It is used especially in the UK, Europe, and former countries of the British Empire such as Australia and South Africa. It is less well known in the US, where A-weighting has always been used.

M-weighting is a closely related filter, an offset version of the same curve, without the quasi-peak detector.