Alright, here's my EMD story...
For many years I've lived, during the summertime, near the Conrail, now CSX, Berkshire Sub, better known as the Boston and Albany or the Boston Line. I have always been curious as to what that EMD humming sound was, and now I hear it less than I did in Conrail days. On those warm, summer nights, the combination of the crickets, the highway, and the rumble of the prime movers and honking of the horn, sometimes accompanied by a rather eerie sounding hum, sometimes quite loud. Now, since CSX usually runs their newest power on the B&A, I hear it less.
It is a warm August night, and I have the windows open. In the distance, along with the crickets and the whine of truck tires on I90, I hear the familiar throbbing of the prime movers of 2 new SD70MACs working upgrade, accompanied by an occasional 14L signal from the engineer's K5LA. The easy beat of the two-cycle 710 has always been a rather soothing sound for me, moreso than GE enginesounds (particluarly the GEVOs -- rather eerie sounding!) and so I start to nod off. Suddenly, from out of nowhere, a loud hum slowly starts to rev up. At first, I wonder if its the town fire siren gone wrong...then I realize that one of those gentle sounding 710s has spooled up its turbo--and now it sounds like a screaming beast! Soon, the other unit spools up its turbo -- and the noise is loud enough that I can hear it over the K5LA blowing at crossings! Then, all of a sudden, both turbos spool down, and once again, all I hear is the familiar EMD throb. Then it is silent as it plunges into state-line tunnel. 10 seconds later, they emerge, but the turbos are both enthusiastically spooling back up. When they are both fully spooled, they are unsynchronized, and it sounds like they are having turbo wars! Finally, the train reaches level ground, and the engineer notches back the throttle as he blows for the grade crossings in town. Aside from that, all I hear is the deep sounding idle of the engines plus the rumble of freight cars. Then all is silent for about five minutes until the engineer slaps the throttle into 8 to ascend the grade through Richmond. The turbos spool up, and for five more minutes, the hum is all I can hear, even when I can no longer hear the prime mover. With the lonely sound diminishing, I go back to bed thinking, "hope those things go to the shop tomorrow morning!"