Railroad Retarder Noise Reduction:Study of Acoustical Barrier Configurations.

摘要

Field measurements of noise were made near a railroad retarder system without barriers and with acoustical barriers of various configurations. The configurations tested included acoustically reflective and acoustically absorptive barriers with heights of 4to 12feet and lengths extending from 0to 22feet beyond retarder entrance and exit. Two of the 12foot high barriers were also tested with a 1foot inward projecting acoustical panel lip along the top. It was found that the absorptive barriers reduced retarder noise from a few decibels inside the barriers to as much as 25decibels at 100feet from the retarder on the system centerline perpendicular to the tracks. Reflective barriers increased noise inside the barriers and at points outside,but near open ends of,the barriers;and reflective barrier noise reduction at 100feet on the perpendicular centerline was limited to about 16decibels. Retarder noise was concentrated in a frequency range between 2and 3kilohertz. The analytical study presented provides details on the role of observer location as well as the various aspects of barrier configuration.