Evaluation of Squeal Noise from the WMATA Transit Car Disc Brake System: A Preliminary Investigation

摘要

The Washington Metropolitan Area Transit Authority (WMATA) rail transit car design adopted the use of disc brakes as the primary friction braking system. Unfortunately, while disc brakes are more efficient than the traditional tread brake designs, they are also prone to generate unpleasant squeal noise. The purpose of this study was to: (1) inspect the WMATA disc brake assembly; (2) assess disc brake squeal noise occurrence on WMATA vehicles and obtain representative A-weighted sound level measurements; (3) identify and evaluate alternative disc brake squeal; and (4) identify future research and development needs relative to disc brake systems appropriate for use on rail transit vehicles. This report states that disc brake squeal is a chronic and pervasive problem on the WMATA rail transit system. It results in a significant increase in operating sound levels during braking (4 dBA) in a large majority of braking operations (92 percent). Although a noise control treatment has been implemented, its effectiveness has not been clearly documented. Conclusions based on the findings of the investigation are presented in this report, and future research and development needs relative to disc brake systems appropriate for use on rail transit vehicles are identified.