音響系統失真測量方式 ITU-R 468 noise weighting

http://en.wikipedia.org/wiki/ITU-R_468_noise_weighting

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)

這與我在這篇 http://records2ear.blogspot.com/2013/06/lp-vs-cd.html  提出的類似
黑色這線是ITU-R 468的曲線，4K~9KHz比重最高，這段也正是那些劈啪聲的主要頻段。
這測法著重在峰值，而非平均值，
峰值呈現的高頻比重多，平均值當然高頻比重就低很多，
高頻的變動快，不容易維持長時間。