Noise reduction measures in Blue Tiger freight locomotives

Mufflers and absorbing blinds were installed in the existing rail fleet as a means of complying with the statutory noise limits for new rolling stock in force in the European Union since 2006 without much investment or development work being necessary.

Initial situation

Havelländische Eisenbahn AG uses three Blue Tiger freight locomotives to transport limestone in Rübeland (Harz). The Blue Tiger is a six-axle freight locomotive weighing 126 tons and fitted with a slow running 2.5 MW diesel engine. It is propelled by six electric traction motors.

Although the enclosed engines and composition brake shoes mean the locomotives are already running at a comparatively low noise level, auxiliary units such as the cooling fan and compressor still generate noise due to the high traction and braking power needed on this extremely steep service line. This has led to complaints from local residents in the past.

Project objective

This project aimed to use three modern freight locomotives to show that the ambitious statutory noise limits applicable throughout the EU since June 2006 under TSI Noise (technical specifications of interoperability relating to the subsystem ‘rolling stock - noise’ of the trans-European conventional rail system) can be adhered to by the existing rolling stock without much investment or development work being necessary.

Technical solution

Mufflers are used to reduce the low frequency suction noise caused by the compressor. Advanced, air-permeable absorbing blinds are used in the cooling chamber to reduce the high frequency noise created by the traction fan and electric brake.

  • It was possible to comply with and even to stay below the statutory noise limits for all operating modes under TSI Noise (stationary, pass-by and starting under load) after modification of the Blue Tiger locomotive
  • The muffler is effective in the low frequency range (80-250 Hz), while the absorbing blinds are effective in the high frequency range above 250 Hz
  • The new absorbing panelling does not restrict operation in any way, such as lower cooling action due to reduced air exchange
  • Unlike before, the compressor is no longer audible when the locomotive is running
  • Instead, the noise it makes is covered by engine noise
  • Noise levels in the cab by the compressor were reduced by a total of 3dB, and in the low frequency range by up to 7dB.
  • The high frequency noise of the fan and the auxiliary units, as well as whistling and howling noises, were effectively reduced by the absorbing blinds


In principle, these noise reduction measures can be applied to other locomotives of this type.

Source: Final report; BMU
Reference source:
Environmental library of the Federal Environment Agency (UBA)
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