Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Building Dana lived in in Ghostbusters was built as an antenna

  1. Sep 15, 2006 #1

    russ_watters

    User Avatar

    Staff: Mentor

    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?
     
  2. jcsd
  3. Sep 15, 2006 #2

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The actual transmitted radio signal certainly does not contain enough power to actually cause a noise loud enough for people to hear on several floors of a building.

    When objects pick up AM radio, they generally have to be very very close to the transmitting antenna, and even then the sound is very soft, often only audible within a few centimeters.

    Any piece of metal will interact with radio waves; that this building has some "impromptu antennae" is not very exciting.

    Personally, I'd be looking for wind pattern correlations first. Lots of buildings can act like giant flutes or organ pipes when the wind blows just right.

    - Warren
     
  4. Sep 15, 2006 #3

    Danger

    User Avatar
    Gold Member

    What if that tiny initial noise got to reverberating in the ductwork? Could that amplify it?
     
  5. Sep 15, 2006 #4

    russ_watters

    User Avatar

    Staff: Mentor

    That's what I was thinking, Danger - couldn't it resonate if the frequency matched the natural frequency of what was absorbing it, warren?

    Wind is a toughie - afaik, when the noise happens, it is relatively constant in volume. If it were wind, it would rapidly change in volume.

    The facilities guys also turned off pretty much every piece of HVAC equipment and the lights in the affected area to try to isolate it and got nothing. Another possibility we were thinking about was an electrical source, like a noisy transformer or ballast, but I don't think the pitch is right for that.
     
  6. Sep 15, 2006 #5

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    What on earth makes you say that?

    - Warren
     
  7. Sep 16, 2006 #6

    Danger

    User Avatar
    Gold Member

    Duh... because as a general rule, wind-induced sounds alter their volume and frequency in proportion to the force of the wind--which is anything but constant.
     
  8. Sep 16, 2006 #7

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    In many parts of the world, wind is actually quite steady. Though it varies throughout the day, it doesn't vary much over the course of a few minutes or even hours.

    I even heard a report on NPR the other day where a woman had recorded the "flute" sounds that her apartment building made -- creepy, high-pitched, and remarkably steady.

    - Warren
     
  9. Sep 16, 2006 #8

    Danger

    User Avatar
    Gold Member

    Maybe we should therefore establish the meteorologic conditions of the location. I have no idea where the hell this building is, or the climatic condition under which this takes place. Where I live, we go from zero calm to 100kph winds in a matter of minutes (it's called a 'Chinook' wind).
     
  10. Sep 17, 2006 #9

    Danger

    User Avatar
    Gold Member

    Sorry... brain cramp on that last post. Got my units mixed up. Chinooks are usually 60 - 80 kph. I've seen them at 100, but it's pretty rare. :redface:
     
  11. Sep 17, 2006 #10

    DaveC426913

    User Avatar
    Gold Member

    Were you a newspaper headline writer in a former career? Way to get 'eyes'. :biggrin:
     
  12. Sep 17, 2006 #11

    berkeman

    User Avatar

    Staff: Mentor

    If it's a radio station, you would need some rectification mechanism to convert it to audio. Like how crystal radios work. I agree with chroot that it would be hard to get a loud sound out of the conversion, unless you were pretty close to the transmitting antenna. Do you know how many of the nearby buildings have radio station transmitters in them? They're pretty common in the city, I'm told. Any chance that there is a transmitter in this building?

    Is there an intercom or PA system in the building? If the radio signal is getting picked up by the PA system, that would provide the amplification needed.

    I was confused by the part where you said your boss picked up radio stations -- what exactly did he do and hear? If he heard radio stations, just listen for a bit to get their call letters, and call them up to find out where their transmitters are. You'd still need to find the rectification mechanism and amplification mechanism.

    Interesting problem.
     
  13. Sep 17, 2006 #12

    russ_watters

    User Avatar

    Staff: Mentor

    The device he used is essentially just a very sensitive amplifier and the microphone pickup is connected to a steel rod. Touch the steel rod to an object that is making noise and it amplifies it. In this case, he touched it to a piece of metal in the building and got a radio station (and identified which one).
     
  14. Sep 17, 2006 #13

    berkeman

    User Avatar

    Staff: Mentor

    COOL. How close is their closest transmitter? What is that transmitter's power level? What is the frequency (approximate is fine if confidentiality is important)? What floor was the boss on when he got that station ID?


    EDIT -- If it's RF pickup, we can spoil that cheaply no problem. Fun problem and solution for the PF.

    EDIT2 -- Adding my HAM License Call ID -- KI6EGL
     
    Last edited: Sep 17, 2006
  15. Sep 18, 2006 #14

    russ_watters

    User Avatar

    Staff: Mentor

    The building is next door to One Liberty, currently the largest building in Philly and it has a lot of transmitters on/in it. The noise is on the 40th floor of a 40 floor building.

    My boss heard the radio station when he touched a unit ventilator under a window (hard connected to the window mullion). He heard a specific radio station (107.5 FM, he thinks), with others evident. Touching the mullion itself, he says there were about 4 stations over top of each other.

    The wierd noise had stopped by the time my boss got there, but the radio noise was evident in two adjacent offices, but not in any other nearby offices (over, under, next-to). So odds are, that was it.
    How do you do that?

    And what could we use to isolate the frequency - and maybe find what direction it is coming from? We don't own a spectrum analyzer, and I'm not sure what I should get....or if it is cost prohibitive.
     
    Last edited: Sep 18, 2006
  16. Sep 18, 2006 #15

    DaveC426913

    User Avatar
    Gold Member

    Stand near it with your arms sticking out. Does it for me on my favourite radio station every time.:biggrin:
     
  17. Sep 18, 2006 #16

    berkeman

    User Avatar

    Staff: Mentor

    I'm thinking of breaking up the conductive path with non-conductive spacers. Like if it's some vertical HVAC conduits that are acting as the receive antenna, then putting a couple non-conductive spacers in would spoil the resonance. If it's the I-beams in the building structure though, that would be more of a problem....
     
  18. Sep 18, 2006 #17

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Hell, attaching a big capacitor or inductor to the resonant metal will screw up its resonant frequency enough to kill its reception.

    - Warren
     
  19. Sep 18, 2006 #18

    russ_watters

    User Avatar

    Staff: Mentor

    One of my boss's friends sent him this news story: http://www.dielectric.com/broadcast/news_story_archive.asp?ID=85
    That's 107.9, FM - the station that my boss heard.

    The floor that the noise is heard on has only been occupied for a year, was unoccupied for a few years before that, and no one remembers it from before then. That fits with the timeline for the antenna upgrade.
    Well, that suggests a possible experiment/fix: if it is the window mullion itself, attachinig a capacitor to it (grounded to the nearest receptacle?) ought to make it stop.
     
  20. Sep 18, 2006 #19
    I think it's the wind thing too. Large buildings have huge intakes for the ac and huge vents as well. They are difficult to keep in exact pace. With a high rise it's not uncommon at all for the overall pressure in the building to be more or less than zero. This could provide a very steady "wind" that is independant of the actual weather conditions. Perhaps the building picks up a vibration on this imbalance.
     
  21. Sep 18, 2006 #20

    russ_watters

    User Avatar

    Staff: Mentor

    Building pressurization is unlikely to be the culprit because they turned off pretty much every piece of mechanical equipment in the area to try to isolate the problem and got nothing.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Building Dana lived in in Ghostbusters was built as an antenna
  1. LED with built-in FF? (Replies: 3)

  2. Antenna Size (Replies: 4)

  3. Coupled Antennas (Replies: 10)

  4. Antenna Duplexer (Replies: 7)

  5. Antenna Basics (Replies: 1)

Loading...