Excessive rail roughness is one of the most significant sources of rolling noise in both heavy and light-rail transport systems. In particular, the noise produced by corrugated track can be perceived as very unpleasant for passengers and communities.
Rail grinding (combined with wheel truing) is the most effective method for reducing noise from excessive rolling noise or corrugation. Unfortunately, the noise reduction offered by rail grinding, which decreases amplitude variations of the running surface, is not permanent. Rail roughness tends to increase after grinding completion; consequently, rolling noise emissions will also increase. Periodic rail grinding, however, adequately controls rolling noise emissions.
Rail condition monitoring keeps track of rail roughness, and rolling noise emission changes over time. Monitoring enables rail operators to identify when and where grinding is most needed, as well as analyze corrugation growth rates. It also allows them to evaluate rail grinding protocol efficacy, particularly as it relates to noise management.
Devices such as RailMeasurement’s Corrugation Analysis Trolley (CAT) measure rail roughness. Unfortunately, it is impractical to measure roughness levels across an entire rail network because CAT’s can only be used on one rail at a time and must operate at a walking speed of 3 – 4 km/hr.
BAP Acoustics offers a unique acoustic rail roughness monitoring service that enables rapid determination of rail roughness at speeds of up to 160km/hr. The monitoring procedure combines CAT measurements, in addition to simultaneously measured GPS and noise data collected at four wheels of a test car. Specialty software, RailInspector, developed by M+P Consultants of the Netherlands, maps roughness profiles across entire networks for both left and right rails. The noise data collected also quickly detects rail squats.
Regular acoustic rail roughness monitoring reduces operators’ costs through ongoing, direct and focused attention on problematic hot spots rather entire networks.