Traffic noise is always one of the main environmental problems in megacities.Middle and high frequency (MHF) components of traffic noises are greatly attenuated by the low-noise pavements,noise barriers and air absorption,etc.,so low frequency (LF) components become dominant.Considering that A weighted sound pressure level underestimates the annoyance of low frequency noises,researchers have tried to assess the low frequency noise with new indicators and amend the relevant limits of environmental noise.This research collected 11 noise samples at the spots 30 meters away from typical traffic trunk in Shanghai,A weighted levels of which were all adjusted to 70dB(A),then 27 volunteers were recruited to assess the annoyance of them.The results showed that the difference between the level of LF band (20~315Hz) and that of MHF band (0.4~20kHz) was highly relevant to the subjective annoyance (R2 >0.85),and when the difference was more than 13dB,over 50% of subjects felt highly annoyed.In addition,noise samples were collected in 13 residential areas along the typical traffic trunk,for which the proportion of LF band energy was over 90%,and the same volunteer group assessed the annoyance of these samples.The results indicated that when A weighted level was more than 56dB(A),over 50% of subjects felt highly annoyed,and as A weighted level increased 1dB(A),the proportion of subjects feeling highly annoyed increased about 20%.Consequently,from the perspective of subjective annoyance,more proper indicator should be adopted to assess low frequency noises,and stricter environmental noise limits should be made to promote peoples satisfaction of environment.