As we go about our daily lives we are subject to a range of noise pollution, especially in urban areas. The Quiet-Track project has set out to reduce some of this ambient noise by ensuring that noise from passenger trains is minimised and maintained at reasonable levels.
By instigating noise calculation procedures the project – guided by its vision for a quieter city – has provided noise mitigation systems which could be used by engineers to maintain or refurbish tracks. The Quiet-Track system looked more precisely at low frequency noise emission and the actual wheel-rail contact, and so offered more accurate measurements, predictions and locations of track decay for remedial attention. New solutions, which included embedded track systems, were developed to achieve noise reduction of at least 6 dB(A) in comparison to current global rolling noise amongst the network of participating infrastructure managers.
The Quiet-Track project concentrated on track situations evidencing significant global ‘pass-by noise’. The system monitored noise generated from the rail wheel interaction in trains travelling at moderate speeds (typically in the range 20-200 km/h). Sound pressure level measurements were taken from in-service trains by two microphones protected by boxes and attached to the wheel apparatus. Additionally, equipment included a GPS receiver, a high precision tachometer (measuring speed) mounted on the axle, a front-end unit and a computer for collating the data. Measurements were transmitted back to receiving units using the internet. The monitoring system could also be augmented with another microphone pair to monitor the track decay rate (TDR).
One of the outputs from the Quiet-Track project was the creation of Noise-related Track-maintenance and Management Tool (NMT). The NMT included a noise mapping tool which detects noise-pollution hotspots and predicted the outcome of noise mitigation efforts. By combining this data with information about the number of people affected in given areas, authorities can make informed decisions about optimum interventions. To help with maintenance the NMT makes available a database of wheel and rail roughness, over time, for every section of the network. Overall increased monitoring accuracy results in more efficiency and cost savings as it reduces the implementation of additional catch-all noise mitigation interventions (such as noise barriers), track inspections as well as prolonging the lifetime of infrastructure.
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