Interface - The Journal of Wheel/Rail Interaction

NOISE & VIBRATION

Reducing Noise and Vibration on NYCT (continued)

Friction control

Lubrication and friction management have also been invaluable tools in reducing noise (and vibration, to some degree), particularly at stations in underground sections of the system. Grease is applied to the gauge faces of the running and restraining rails to control wear and reduce screech and squeal on sharp curves. For a heavy rail rapid transit system, NYCT has its share of sharp curves, many of which are 350-foot radius or less. The average noise on one 180-foot radius curve at the South Ferry underground station, for example, was 109 decibels—even with grease applied to the gauge faces of the running and guardrails. With trains operating at two-minute headways at times, the noise bordered on unbearable. A water spray treatment reduced the noise levels to 90 dBA, but degraded the ties and corroded the rails very quickly.

This convinced NYCT to adopt the use of Kelsan Technologies' KELTRACK® top-of-rail friction modifier. This, in conjunction with gauge-face lubrication, reduced the noise levels to 85 dBA, offering better noise attenuation properties than the water spray, without its detrimental effect on the track structure, Cabrera said. Other tests of top-of-rail friction modifiers on a 300-foot radius curve on a 3.8% ascending grade showed a maximum average noise reduction of 7.3 dBA (an average 5.2 dBA in the 31.5 - 200 Hz frequency and 13.3 dBA in the 1,000 - 20,000 Hz frequency). Top-of-rail friction modifiers also appear to moderately reduce vibration (by 3 - 5 dB at 31.5 - 200 Hz), he said.

Only by looking at all aspects of the system—vehicles, track and operating conditions—NYCT has been able to effectively reduce noise and vibration on the system.

This article is based on "Maintenance and Noise Abatement Programs at New York City Transit," a presentation by Antonio Cabrera, Director of Track Engineering, New York City Transit, at Interface Journal and Advanced Rail Management's Rail Transit '04 Wheel/Rail Interaction Seminar.

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