Noise (and vibration) from MY Rapid Transit (MRT) trains during future operations of the MRT line(s) are primarily generated from the rolling interaction of the wheels with the rails. Additional noise may be generated from brake squeals during braking at the stations and curved segments of the rail alignments.

In the underground sections of the alignment, vibration from the tracks shall also transmit in the soil manifested as ground-borne vibration and noise.

The vibration may be perceived as feelable vibration in extreme case, and more likely perceived as low frequency rumbling noise.

Comprehensive noise and vibration analysis are undertaken to determine noise and vibration levels along the entire MRT alignment to ensure that noise and vibration levels shall comply with Department of Environment (DOE) approved limits.

The analysis involved comprehensive computer based environmental noise modelling using state of art software that had been used in other major MRTs in the world.

These analyses are used to identify and to design noise and vibration mitigation measures for the entire MRT project.

The analysis and detailed design of the control measures are undertaken by the Institute of Noise and Vibration, Universiti Teknologi Malaysia being the independent noise and vibration consultant appointed by the project delivery partner (PDP) for this project.

This Institute is the country's leading authority in noise and vibration.

The mitigation measures for noise and vibration control during MRT operations consists of a combination of the following:

- Noise barriers, semi and full acoustics enclosures;

- Platform tracks acoustic absorption;

- Continuous welded tracks;

- Low vibration track-forms (tracks with high performance vibration isolation elements) in sensitive locations;

- Resilient pads at not so sensitive locations; and

- Periodic maintenance of rolling stock and tracks (wheel and rails grinding).

The noise barriers, semi and full enclosures shall be installed on the guideways of viaducts (elevated box girders forming the guideways) fronting all noise sensitive receivers at locations that may potentially be affected by MRT noise.

These barriers and enclosures function in a manner where it either shield and/or partially or fully enclose the trains and rail tracks such that the noise do not propagate directly to the receivers of concern.

Semi and full enclosures are typically used in locations where high rise apartments and buildings with residents located higher than the tracks which would have a direct line of sight to the tracks in the absence of such semi or full enclosures.

Low vibration track-forms and resilient pads function in such a manner where vibration from the wheels tracks rolling action are dampen (attenuate) through a vibration isolation element or resilient medium.

It behaves in a similar manner as a shock absorber in a car with dissipation of the vibrating energy through the isolation element or device.

The low vibration track forms are primarily used in the underground sections of the MRT alignment, and at the elevated viaducts that are in close proximity of houses and buildings, and noise and vibration sensitive areas.

Identification of locations requiring mitigations and design requirements of these measures are established from the noise and vibration analysis undertaken by Universiti Teknologi Malaysia. These measures shall be incorporated into the design and construction of the MRT project.

The design of the viaducts structures and track works are such that noise barriers and enclosures and low vibration track-forms respectively are planned in such a manner that additional up-scaling or use of these measures can still be implemented even when the MRT system is in operations.

This in particular relates to instances where mitigation measures may have to be introduced at areas where the adjacent land use of the alignment is currently not developed at this point in point or alternatively may re-developed in the future.

While it appears that there is apprehension of potential noise (and vibration) concerns amongst the general public particularly at locations in close proximity to the MRT alignment, all parties involved in the planning, design, construction, supervision and administration of the MRT project are mindful to the concerns and issues on hand.

The above described measures represent a conscientious attempt to manage and minimise the generation and the propagation of noise and vibration from the project by all parties involved in the project, and in particular the project delivery partner and MRT Corporation.

 

SALMAN LEONG is professor/director of the Institute of Noise & Vibration at Universiti Teknologi Malaysia.