Fig. 2From: Effect of GRM7 polymorphisms on the development of noise-induced hearing loss in Chinese Han workers: a nested case-control studyThe proportional distribution of the binaural average hearing threshold levels (HTLs) at 3Â kHz,4Â kHz,6Â kHz in case and control groups. HTL is grouped by 5Â dB(A) in both case and control groups. The control group ranges from 0 to 35Â dB(A) and the case group is in the range of 40 to 85Â dB(A)Back to article page