So I'm sure you all know that the building Dana lived in in Ghostbusters was built as an antenna for psychokinetic (or whatever) energy, focusing that energy on the 13th floor... Well, I was in a new client's building in Philly a couple of days ago and the facilities guys took us to one floor (near the top of an ~40 floor building, but I'll check specifics Monday) to see if we could help identify the source of a strange noise people were hearing. The people in the office actually refer to it as "the ghost of [insert building name]". They also describe it as what it would sound like to stand inside a tuning fork. The noise wasn't evident while we were there and there has been no identifiable pattern to it - it comes and goes for hours, days, or weeks. It is loud - it can be heard on several floors at its worst. I think it is high frequency, though I'm not sure what frequency yet. It seems to emanate from everywhere. They called my boss this afternoon when it started up and he went down with a device that picks up and amplifies very soft sounds on objects (it is just a little metal probe on an amplifier, with headphones) and touching it to metal objects like ductwork, window mullions, etc. (again, I'll find out specifics when I go into work on Monday), he found that it picked up radio stations - fm, 100something mhz. Now the possibility that it was picking up radio waves was something we had considered and mentioned to them on our first visit, so we got some instant credibility, but it is is a long way to go to figure out exactly the source and how to fix it. I was thinking perhaps that the carrier wave itself was oscillating in something, causing it to vibrate. But fm radio is too high frequency (human hearing is up to about 20khz, fm is ~100 mhz). It could be some sort of low freqency radio communications, or perhaps some harmonic of another frequency. The building is somewhere around 50 floors - perhaps 700 feet, which puts it at about the right size to pick up AM radio. Anyway, we are going to get ahold of a spectrum analyzer to try to pinpoint the frequency we are dealing with, but anyone ever deal with this phenomena before and know what it could be and/or how they might deal with it?