Outside of the more specific train related items on Active's links above.
Ever hear a generator engine sound change when a heavy load is applied, or changed dramaticaly? RPMs dont change much on generators with precise Hz/RPM fuel controls, but the sound changes due to the loading of the engine, and the fuel mixture to maintain that RPM. Sounds like its rev'ed up. More likely that the gate (choke) to the turbo charger is opened up more, introducing a high pitched whine. And exhuast compression is higher.
During proper maintanance of generators it's required to
\"load bank\" the gennie to reduce "wet stacking" of the engine and exuast systems. When you do this, you control the load applied to the gennie stepping up to ~80% of rated load. (And run it hard for several hours) But as you step it up, you'll get a good feel for pitch change vs. load, but RPM's have not changed much. At no load it may sound like a high idle, at full load it sounds like a semi charging down the freeway. Or a train leaving the station....
[This message has been edited by e57 (edited 01-14-2006).]
