By Mr Francis CHAN 
Railway, one of the conventional modes of transport, has greatly facilitated the daily life of people. However, constructing a noise-abating railway system is always a challenge to engineers. In the technical meeting on 1 September 2005, organised by the CV Division and chaired by Ir Prof Andrew Leung, Ir Richard Kwan from KCRC generously shared their experience in tackling this thorny problem.

In Ma On Shan (MOS) Rail, the trains operate through the centre of the Ma On Shan and the alignment of rail, which is surrounded by the high-rise buildings. It is not difficult to understand that "once you see the railway, once you hear the noise" when you are there. The impact of noise produced by railway infrastructure needs to be controlled. Therefore, a series of mitigation measures have been developed to reduce the noise impact on the high-rise receivers.

The MOS Rail is mainly constructed as the floating slab trackform system, in which the slab tracks are supported by the rubber bearings on the viaduct. The system could largely reduce the radiated noise and the noise generated from the vibration of support.

Ir Kwan said that another noise mitigation measure in the MOS Rail is the enhanced multi-plenum system. The original multi-plenum system is to perform numerous defending rings for trapping most of the noise: the vehicle skirts are placed at the bottom of the train, acting as the first line to alleviate the noise generated between the wheels and the rail. The central plenum and the noise absorption material sprayed under the walkway help to seal the noise from the alignment. 

Engineers never hesitate to develop new and perfect technology. The enhanced multi-plenum system has been designed and applied in the MOS Rail. The rail noise absorbers, specially designed with polycarbonate made, are sandwiched in the rail to further reduce the noise generated from the wheels.

Since the multi-plenum system could not be installed effectively at the turnout, two enclosures were thus built in Heng On and Wu Ka Sha to implement noise mitigation.

During the question-and-answer session, Ir Kwan remarked that engineers not only solve technical issues, but also help establish a good public relationship with the community. After proposing a vote of thanks to the speaker, Ir Joseph Choi presented the souvenir to Ir Richard Kwan.