Highway tunnel noise reduce case studies

The reverberation time and noise level of tunnel-typed public works can be reduced by adding large amount of acoustical structure with high absorptive coefficient.These absorptive structures can be applied on the curved wall and track bed.After applying the CEMCOM acoustical material,the reverber-ation time was reduced about 64%~84% and the noise reduction level was predicted about 4.7dB~8.5dB in the measured 1/3 octave bands for the Guan-Kou-Ya tunnel of Chang-Zhang highway,Hunan Province.Especially,the predicted noise reduction levels are about 7.1 dB to 8.5 dB between 200 Hz and 800 Hz in the measured 1/3 octave band.Using a noise spectrum from a current express way,the noise reduc-tion level is predicted about 6.3 dB(A) and the speech interference level is reduced about 6.6 dB.