Outside Salmon Arm, BC, trains travelling west on the Canadian Pacific Railway ascend Notch Hill, a 1 degree incline with a 6 degree–radius horseshoe curve. The curve is so tight that a longer train will pass by its own railcars after turning the corner. In 1995, CP Rail introduced new General Electric 9500 Series locomotives to haul heavy loads of coal and grain westward to the Port of Vancouver. But when the new diesels took to the rails, residents living near Notch Hill began complaining about annoying ringing noises. In the summer of 1996, CP Rail hired BKL to investigate the ringing and recommend possible solutions. An acoustician visited Notch Hill and made a series of short- and long-term measurements onboard trains, near the tracks, and in the community. The goal of the study was to identify the source of the nuisance noise, determine its tonal characteristics, and find out if the noise was linked to a specific operating condition. To that end, throughout the study, BKL's acoustician tracked and analyzed the various train setups, locomotive models, and loads. In addition, BKL compared the measured noise levels to the sound levels allowed under regulatory limits, including regional nuisance noise bylaws. After gathering substantial data through its on-site assessment, speaking to residents in the community, and meeting with engineers from CP Rail, BKL analyzed its findings and connected the ringing sound to the locomotives' throttle settings and the locations of lubricators along the track. Additionally, CP Rail engineers identified that one particular lubricator was delivering more grease than others. This lubricator was located near the beginning of the horseshoe curve. To climb Notch Hill, train engineers had been setting their locomotives to maximum power. BKL's study found that running the engines at full throttle, along with other factors including increased rail grease, caused the locomotive wheels to slip and spin—and emit that pesky ringing noise. BKL suggested optimizing the locomotive's power output on the climb, and when CP Rail implemented the recommendations, the ringing noise ceased. Furthermore, climbing the hill in a lower throttle setting created less wear on tracks and wheels. The next year, when CP Rail was considering new GM locomotives, they hired BKL to conduct a follow-up study in the community. BKL measured noise from various locomotive configurations, confirmed that noise emissions wouldn't exceed local bylaws, and then commented on the findings. By conducting two in-depth noise assessments, BKL helped to identify and solve a nuisance noise, while also ensuring ongoing positive relationships between CP Rail and nearby communities. Have a project in mind? Get in touch today.