Originally Posted by Mike CT:
Interesting to note that several of the diesel emergency stand-by power supplies, that I have installed, had exceptional silencing equipment. Containment housing and mufflers, all designed for a hospital/nursing home setting. Maybe those high horsepower on steel wheel units could be a bit more quiet. 
For what it's worth, EMD locomotives have had exhaust silencers since about 1972, plus redesign of cooling fans, all to reduce noise per AAR/FRA mandates. Pretty sure that GE has had to go through the same redesigns for reduction of noise.
