Fri Oct 27, 2006 12:01 am
Um, there aren't any warning sirens in New York. I work there building things.
They brought in a Modulator to put at Ground Zero during the cleanup in case they tried anything else.
Since that's a subway, and since I've heard a zillion of them, I'm going to take a stab that you're hearing one of the old-style AC/DC rectifiers. They make an ungodly howl. The rectifiers take ConEd power and turn it into DC power (600 v at 3,000 amps) to run the train.
I did a rehab at a TA substation in Harlem and thought I'd lose my mind listening to the only old-style rectifier still in the building. At least it wasn't one of the even older mercury-arc rectifiers. All the old rotary style ones are gone.