Abstract: The objective of this study is to reveal the cause of noise annoyance originating from its perceptual properties. The available temporal factors extracted from autocorrelation function(ACF) were used to explain the primary sensation and representative perceptual property of road-vehicles sounds,considering its physical characteristics.Two novel factors EMD and ESM,used especially for measuring fluctuation and smoothness of the ACF envelope,were proposed.It must be pointed out that if φ₁ was not the maximum value except φ(0),φ_max andτ_max were supposed to be added.Three primary sensations-loudness,pitch and timbre have been acquired by applying the principal component analysis to ACF factors,extracted from 232 noise samples.From 10 subjects,annoyance scale values caused by these samples were investigated using magnitude estimation under well-controlled experimental conditions.From our experiment,the authors came to realize that there certainly exist elementary factors for describing the primary sensations.Different ACF characteristics can cause diverse dominant sensation,which would control or determine the perceptual properties of the noise.The variability of dominant sensation and the priority difference in primary sensations bring about noise annoyance.Moreover,mixture of elementary factors from different primary sensations would lead to confused auditory sensation,and also a source of noise annoyance.In other words,it is the chaos of perceptual properties,which cause and affect annoyance.