Chief Allan Graves called it the "Symphony of the Engine Room". It's not loud; you can carry on a conversation at normal volume while standing next to the engine. If you listen, you can pick out the individual notes, just as if you listened to an orchestra. Of course, you have the engine, with its ever changing voices. There is the constant whirl of the fuel pump, and the background, muted bass of the generator. The condensate pump makes a steady "chk chk" as the shuttle valve works back and forth. The circulating pump gives a drum beat. Oddly enough, the loudest thing is often the condensor, which has no moving parts. Who would have guessed that turning steam into water could be so loud?

As you gain experience and can pick out individual things, you can use the sounds of the plant to tell you how things are operating. For example, there is a check valve on the feed line to keep boiler pressure from pushing back against the pump. When feed water is going into the boiler, it rattles, making a grinding sound that alarms some folks. However, this grinding sound is a great thing to hear as it means there is feed water going into the boiler. Even the engine's sounds can tell you things. The thing I listen for the most is the engine telling me it needs oil.