You guys want to talk about diesel unit sounds? Well my favorite is the UP DDA40X, which was the highest HP EMD prime mover ever produced WITHOUT any exhaust silencer (muffler to you guys). There is no other diesel locomotive ever produced in the U.S. that equal the total sound volume and "sound note" of those twin 645E3A turbocharged engines at 900+ RPM.
Naturally, MTH has yet to effectively reproduce THAT sound on their DDA40X models.
Allow me to second that. I saw 6936 only once, she surprised me one morning charging up the UP Milwaukee Metro line out of Chicago with about 4 of the heritage cars in tow. Even though she was loafing, I could tell something different was coming and THERE SHE WAS hustling up Greenbay Rd through Wilmette. You're right Hot Water and WHAT A SOUND! Wish I could seen my face coming outa that pancake house! Before I could take it all in...she gone!
An interesting side story; during the weeks prior to the big 50th Anniversary of the EMC/EMD FT demonstrator (1939 to 1989), EMD was accumulating all the various different locomotives that would be on display for the "Open House" celebration (October 1989). Naturally the UP sent DDA40X #6936 for the big event. However, the 6936 arrived facing the wrong direction! The EMD Traffic Dept. was quickly informed, that we would need the IHB to come to the McCook Plant, and take 6936 north to Proviso Yard, proceed around the wye interchange, and bring it back to EMD.
One problem. DDA40X 6936 was not running, and the IHB was simply going to send a crew to EMD, and run it up to Proviso Yard, and run her back. The batteries were dead on the 6936, as someone had shut both engines down, and left the battery knife switch in, which drained. the batteries! So,,,,,,the Engineering Test Dept. brought a welder out to the unit, and charged the batteries enough to start both engines. A suggestion was made to "Lets put both engines on full self load test, and REALLY recharge the batteries!". What with all that fantastic exhaust noise, sitting just outside the main Engineering Building, it didn't take long for all sorts of Engineers, Managers, Secretaries, Janitors, and hourly workers to exit the building to see just what all that deep "noise" was. Literally dozens of employees began to gather around, as 6936 produced her fantastic music! Many of the senior employees pointed out that, "THAT's what locomotives are supposed to sound like!".