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Ashmont Noise Mitigation Project
Update #3 (May 16, 2011): Since the last update, the MBTA reached a successful conclusion in its efforts to mitigate the noise at the Ashmont Loop of the High Speed Line by reducing both the peak sound levels and the duration for which these levels occur. This success was achieved by testing both secondary and primary corrective actions.
The secondary corrective action includes an onboard low volume spray system and a wheel mounted rubber dampeners. The MBTA implemented these actions as an integrated system. The system has been tested and achieved desirable results. The MBTA will be monitoring the system during routine vehicle inspections.
The primary corrective action is a Schrey & Veit (S&V) tuned wheel vibration absorber. The S&V finalized the design of the absorber. It has been tested and achieved desirable results. The MBTA plans to implement the absorbers as the permanent long-term sound mitigation solution. Currently, the MBTA is procuring the S&V tuned vibration absorbers and will install them as part of a fleet conversion.
For further information about our ongoing efforts, please feel free to contact Gary Campbell Director of Light Rail Maintenance at GCampbell@mbta.com.
Update #2 (March 10, 2011): Since the last update, the MBTA has been working diligently at finding feasible solutions to mitigate excessive wheel noise at the Ashmont Loop. During that time, we examined and tested several viable solutions to address this concern.
Currently, the MBTA is testing a rubber dampener, which is applied with a special adhesive that adheres to each wheel and withstands temperature fluctuations. Simultaneously, the Authority is testing an additional prototype solution, an onboard spray system, which will work in tandem with the rubber dampeners. The spray system is operator activated.
When employed together, both of these prototypes have had encouraging results Procurement of the materials to implement both solutions is underway and installation will take place upon arrival.
In parallel, the MBTA is investigating another possible solution that uses a modified wheel with a mechanically bonded noise dampener. A machined wheel analysis determined that this proposed solution is safe for prototyping. The Authority is presently milling grooves in the wheels to reduce vibration and mount the dampener assembly. The MBTA anticipates testing the solution this summer on the Mattapan Hi-Speed Line.
For further information about our ongoing efforts, please feel free to contact Gary Campbell, Director of Light Rail Maintenance, at GCampbell@mbta.com.
Update #1 (December 10, 2010): Over the last few months, the MBTA has been working diligently to mitigate the noise emanating from the interface of the wheel and rail at the Ashmont Loop. In the spring, the MBTA took the immediate step of installing a sprinkler system that watered the rail during all hours of operation. Although successful in reducing the noise, the MBTA never believed that this measure would be a long-term solution to mitigating the noise.
The MBTA is looking at a number of other stopgap solutions. Recently, the MBTA tested a sound absorbing film that adheres to the wheel. The test of this product at the Authority’s Everett Shops Facility revealed a minimal noise reduction. Through the testing process, the MBTA found that permanent adherence of the film to the wheel may be difficult given the temperature fluctuations during the year. The MBTA is also testing a sound absorbing “donut” that adheres to the wheel. The testing of this product at Everett has been more promising. The MBTA is currently in the process of determining how best to adhere the “donut” to the wheel. Once this matter is resolved, the MBTA plans to conduct a field test at the Ashmont Loop to measure the reduction in noise from the “donuts” being placed on the wheels.
Additionally, the MBTA is looking into several other possible long-term solutions. The MBTA is in the process of procuring a new type wheel with noise dampeners, which will potentially reduce sufficiently the noise from the Ashmont Loop. The MBTA is hoping to have the wheels delivered, machined, and installed by next summer.
To get more information about the process of determining a feasible long-term solution, please feel free to contact Brian Dwyer, Director of Light Rail, at email@example.com.
Initial Posting (August 1, 2010): The MBTA conducted sound measurement testing on the PCC Trolleys on Saturday June 19, 2010 and Friday June 25, 2010 as the trolleys operated on the turn-around loop at Ashmont Station. The measurements were taken at five locations, three public locations: Beale Street, Radford Lane and Dorchester Avenue and two locations on MBTA property: center of loop and the station platform. Please see the site map in the July 20 presentation.
The measurements taken on June 19 were needed to establish the baseline noise of the trolleys as they operating over the Ashmont Loop. Additionally on June 19 after the baseline measurements were complete, several measurements were taken of trolleys operating on the turn-around loop with the track water misting system functional. These measurements were used to determine the mitigation impact of the misting system.
The measurements taken on June 25 were to quantify the impact of the all of the short-term mitigations steps taken by the MBTA in place: water misting system, noise attenuation blankets, and operating rules compliance. The results of the June 19 and June 25 measurements indicate a significant reduction in the noise of the trolleys as they operate around the turn-around loop. The mitigation actions taken were successful in significantly reducing the maximum noise levels but just as importantly the duration of the noise.
The results of the measurements are part of the presentation titled “Noise Measurement Results at MBTA Ashmont Station” (please see separate link).
- Station Master Announced
- Presentation - July 20, 2010
- Presentation - March 23, 2011
- Presentation - May, 16, 2011
What causes the noise?
The high frequency tones radiate out from the steel wheel riding over the steel rail in the curve similar to a making a wine glass ring by rubbing your fingers around the rim with water.
What do the measurements do for us; we know the trolleys are too loud at Ashmont?
The baseline measurements taken and their associated sound analysis will be used by the MBTA as source information to identify and evaluate long-term technical solutions.
What Instrument did you use to do the measurements?
The instrument we used to measure the noise was a Bruel & Kjaer 2250 Sound Level Meter (Type 1). The instrument was calibrated on September 11, 2009. Please see the presentation titled “Noise Measurement Results at MBTA Ashmont Station” (please see separate link).
Why is it important to know what frequencies make up the noise?
As part of the measurements taken on June 19 and June 25, the MBTA analyzed the sound recordings to break up the sound into its parts. This analysis was presented on July 20 in the slide titled “Wheel Squeal Spectra”. This process is very similar to breaking light up into a rainbow of colors with a prism except in the case of sound the parts are made up of sound at different frequencies. The analysis of the sound measured without any mitigation showed us that the primary source of the wheel squeal is 4,100Hz. This information will be used in identifying long-term solutions to mitigate the trolley noise.
Based on feedback received at the community meeting held on July 20, 2010, General Manager Davey has designated Red Line Transportation Supervisor Tom Crowley as the “Station Master” for Ashmont Station. As a Red Line Transportation Supervisor, Tom oversees all aspects of Red Line Operations. Tom is a 12-year veteran of the MBTA. He started his career as a part-time streetcar motorperson in Light Rail Operations in 1998. Tom has extensive experience in construction coordination at the Authority. His additional duties will include serving as an ombudsman for customer concerns related to Ashmont Station – Red Line Operations, Bus Operations, Light Rail Operations (PCCs), and on-going issues related to station renovations.
Tom can be contacted via email at firstname.lastname@example.org (this is our preferred method of providing feedback to Tom). Tom can also be reached at the Red Line Transportation Superintendent’s Office at 617-222-5099.