Loudest steam engine I have ever witnessed.....and I have seen plenty of steam engines, including PM 1225, just this weekend, and the 1225 is a loud-mouth herself.
A couple of years back, Pete Lerro ran a charter on the R&N with the 425. We were in the Lehigh Gorge during a snowstorm, and the engine was out of view around a curve. The stack beats were so close together and were echoing off the canyon walls, producing just a steady, loud roar. One of my photographer colleagues is a Navy Flight Test guy and we just looked at each other. We couldn't decide if we were about to be buzzed by a KC-135A with water injection, or an F-4J in full blower. It sounded for all the world like an approaching military aircraft at very low altitude.
Here is the shot I took of the "Blue Pacific" on that pass:
425 in the Lehigh Gorge
/Kevin Madore