Exhaust noise control case study for 2800 class locomotive

In NSW, Environment Protection Authority Licences for railway systems activities define noise limits for locomotives applying for permission to operate on the network. This paper describes a case study involving one particular locomotive class (the 2800 class) that had been refused permission to operate in NSW on the basis of low-frequency noise emissions. This paper describes investigations into the locomotive noise and muffler performance, and the steps taken to re-design the muffler to optimise its performance. The objective was to reduce low frequency noise emissions to comply with the EPA licence requirements. The project achieved a reduction in overall Lmax noise levels of up to 5 dB in the highest engine notch settings. The low frequency benefit (in the 25 Hz and 50 Hz one-third octave frequency bands) was of the order of 8 dB. The locomotive class has subsequently been granted approval to operate in NSW.