Yeah, I like that CN recording. The fastest freight train I've recorded.
About the GP11's sounding like helicopters--couldn't agree more! Someone actually mistook a GP11 for a helicopter in one of my recordings! This one, actually--LLPX GP38-2 2232 and SLR GP11 8749 in run 8. (2232 also has a blasty Nathan M3H horn, which has since been replaced)
http://trainiax.0catch.com/slroct2000.wav
Gosh, I love that GP11...
Here's another one of my favourite EMD sounds (well, I like them all...) Halfway between the chugging Paducah Geeps and the deep 40's are the 38's--a few years ago SLR leased a fleet of ex-LIRR GP38-2's, freshly rebuilt, from LLPX. Those had perhaps the "cleanest" sound of any units I've heard--I think their reliability was bulletproof and they were in excellent general condition. They always ran in perfect harmony and sounded identical as they passed. Here are 4 of them...
http://trainiax.0catch.com/slrapr152001.wav
As for the 40's, there's more than one whine that they make. There's the fan whine which can usually be heard when they're close, but there's another whine, which can be heard for much greater distances. It's slightly higher pitched and a less sharp sound. You can hear it for most of the recording below, but the whine of the fans can only be heard once the units pass. I don't know what this other whine is--maybe the traction motor blower?
http://trainiax.0catch.com/slrmar1405-3806.wav
By the way, this recording is of SLR GP40M-3 3806 with a road slug and a GP40, crawling upgrade at 10 mph--slow enough that the oscillating ditch lights stopped flashing between the first and second whistle blasts!
The construction of the 16 cylinder and the 20 cylinder turbochargers for E3 engines is quite similar. The 20 cylinder has a little larger compressor diffuser area and with the greater exhaust flow it is able to wind up to considerably higher RPM in the top throttle notches. This contributes significantly to the difference in sound, both in amplitude and frequency.
I don't think the RPM of the 20-cylinder is different from the 645--both "standard" versions max out at 900 rpm, while the tweaked versions run at 950 rpm. Having said that, it's true that the sound is quite different--and it's because of the number of cylinders. With 25% more cylinders in the 20-cylinder version, it should create a pitch 25% higher than a 16-cylinder engine at the same rpm--which is, in fact, the case. I've never heard a 20-cylinder 645 in person, but I have heard a recording--a cool sounding engine indeed! It also makes sense that 20 cylinders would make more noise than 16.
Metro-North FL-9's had 5 chime horns that were absolutely the sweetest sounding horns ever. You could be on either side of the Hudson River and when they blew those horns you'd hear the initial blast, then a very melodic echo as the sound traveled across the valley.
The FL9's used to have Hancock 4700 air whistles that imitated the sound of a steam engine, that were later replaced by the (now commonplace) Nathan K5LA. The K5LA is particularly melodious when in tune!
I probably should have been more specific; when I refer to the EMD "whine," I'm also thinking of the "whistle" sound that comes from the turbo, which is definitely not something you hear from a GP38 or other non-turbo EMD loco.
Right on! I like the whistle, a defining sound of any turbocharged loco.