||Tri-County Metropolitan Transportation District of Oregon, Portland.;Transportation Systems Center, Cambridge, MA.;Urban Mass Transportation Administration, Washington, DC. Office of Technology Development and Deployment.;Environmental Protection Agency, Washington, DC. Office of Noise Abatement and Control.
This document presents instructions on how to apply a noise treatment to a contemporary city transit bus without extensive structural alteration. Baseline bus configuration, noise ratings, and performance benchmarks are presented for a Flexible 111DC-DO61 transit bus powered by a Detroit Diesel 8V-71N engine. The concepts and much of the hardware described in this report are transferable to similar buses. The information presented herein is of interest primarily to transit bus operators wanting to reduce noise by practical means, and to government agencies, manufacturers, and planners concerned with reducing the noise of buses in service at a moderate cost. In this report instructions are given on how to retrofit the engine with a turbo-charger and ancillary hardware. Acoustic benefits and performance side-effects are given. One beneficial side-effect, because of turbo-charging, is reduced harmful exhaust emissions. Another, because of smaller injectors and reduced exhaust back pressure, is fuel conservation. The instructions in this report are complete with sources for manufactured components and raw materials, and with mechanical drawings for components to be locally fabricated. Illustrations and text direct installation as well as effects of noise ratings and performance side-effects are also presented. In this report practical application is coupled with theoretical explanation throughout.