Development of passive and active noise control for nextgeneration locomotive cabs

摘要

The noise environment in a locomotive cab has been the focus of recent attention by the FederalRailroad Administration (FRA). In October 2006 the FRA established a new rule to amend itsexisting occupational noise standards for railroad employees whose predominant noise exposureoccurs in locomotive cabs. The noise exposure rule is expressed in terms of the A-weighted noiselevel and is consistent with OSHA limits set for general workplace noise exposure. Recentstudies have shown that low-frequency sound can be an important contributor to noise inducedhearing loss as well as fatigue. Therefore the focus of the FRA rule on the A-weighted noiselevel may not be enough to guarantee a fatigue-free cab environment where low-frequency soundsources are dominant. This paper describes the research project sponsored by the FRA todemonstrate the feasibility of a combination of passive and active noise controls in the cab ofnext generation locomotives. A mock-up of a locomotive cab was used to demonstrate thefeasibility of active noise control to reduce the low-frequency noise levels. The active noisecontrol system focused on eliminating key pure tones that are typically found in the noisespectrum from a diesel engine.