Why do city buses sound different?

YOU ASKED:What causes our municipal buses to have such a distinctive sound? My mechanical knowledge doesn't extend much beyond being aware there is a motor and a transmission in there somewhere.

- Gerry McRae

OUR ANSWER:Our mechanical knowledge doesn't go any further than yours so we enlisted the expertise of Norm MacLeod, maintenance manager for the Kamloops Transit System.

We also did some online research about municipal buses and the noise they make.

First off, the engines are diesel, which tends to make the buses louder than the average gasoline engine just because of the compression-ignition nature of the engines.

Whereas gas engines (spark-ignition engines) get most of their noise from the exhaust system, which is controlled by a muffler, much of the characteristic whirring/whining/rattling sound of a diesel engine comes from the engine itself.

In the case of Kamloops buses, "the noise is caused by the motor and transmission being positioned at the rear of all our bigger buses with no soundproofing to make it any quieter (like a passenger vehicle)," said MacLeod.

"So any noise it makes is very noticeable."

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