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Acoustics? (Yet Another IB Extended Essay Thread)

  1. Aug 23, 2007 #1
    Hi there,
    I'm sorry if this sounds incredibly vague, but I'm having difficulties narrowing down the research question for my Physics EE.

    I'm sure of the field I want to do it in: acoustics. The problem with most experiments involving applied acoustics (ideal room sound, etc.) is that, unless you have extremely expensive measuring equipment (which I don't; though I do have a collection of fairly "alright" condenser microphones), the results you end up with are pretty much unusable.

    I was toying with the idea of doing something in psychoacoustics at first, but I found those topics to be incredibly complicated, subjective and more often than not ranging too far into other subject areas (anatomy, computer science, psychology). An example of this would be attempting to quantify intelligibility (of PA systems, etc.) using an algorithm. Much too complicated, not physics-y enough.

    Extended Essay examiners tend to be partial towards original, even obscure topics. I came across an experiment in an acoustics textbook that would fit these criteria perfectly: an upside-down parabolic reflector with an ultrasonic whistle at its focal point is used together with a reflecting glass plate to create standing waves with enough intensity to levitate small pieces of cork! This is the sort of thing I'm looking for. The obvious problem with this particular one is that (while incredibly cool) it doesn't really have any sort of research question associated with it.

    So there you have it. I'm in a bit of a rut, as you can see. Sorry for the long-winded post, but I'm slowly getting desperate. Any realistic ideas or pointers in the right direction would be incredibly appreciated.

  2. jcsd
  3. Aug 23, 2007 #2


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    Staff: Mentor

    Just some ideas off the top of my head:

    ** Look for a new use of noise cancellation -- what are some of the more creative places that active noise cancellation is used in now? What other applications can you think of that might not have been thought of yet?

    ** Maybe make a sensor circuit and sound pickup arrangement, so that you can mix in outside sounds with 3-D directional qualities for people who are wearing headsets. Like the folks in fire engines, especially the driver -- they wear full earmuff-style headsets so that they can hear each other over the siren. But it would be cool if you could have microphones outside the engine, and cancel out the sound from the sirens, and transfer the outside sounds into the headsets with 3-D qualities. So when they turn their head, the sound changes to help them locate the source in 3-D. Like when they roll up to an incident, and people try to talk to them through the windows, for example. Are there other places where people with headphones could benefit from hearing outside sounds in 3-D, maybe with noise cancellation of whatever has them wearing the headsets in the first place?

    ** Is there some way that you could make a device that skin divers and scuba divers could wear, to give them back 3-D sound? When you're diving, you can't really tell what direction a sound is coming from. What are the reasons for that, and can you make something like a light, comfortable belt-mounted somethingorother that picks up sounds, and processes them and transfers them to comfortable underwater earphones to give the diver 3-D awareness of sounds?

    ** have to think about this some more....
  4. Aug 23, 2007 #3
    Sometimes the same technology can be repositioned: Bose made some noise-cancelling headphones, and found that the same idea could be used to make an "active" car suspension, allowing cars to drive over speed bumps at high speed.

    [1] http://www.bose.com/controller?even...g/project_sound/suspension_challenge.jsp&ck=0
  5. Aug 23, 2007 #4
    if this comes in acoustics:
    > in space
    > over long distances.
    > between humans and computers

    -the use of ultrasound for medical diagnosis

    but I think this also brings in E-M waves...
  6. Aug 23, 2007 #5


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    Staff: Mentor

    I'm not tracking... acoustics communications in space? I must have misunderstood what you were trying to say. Could you elaborate?

    BTW, Quiz Question -- there is a way you can communicate between space ships using acoustics and no physical connection -- what is it?
  7. Aug 24, 2007 #6
    I don't know much about acoustics, so just made a vague random shot.

    but it's not "acoustics communications in space"
    rather I was asking that if communications in space come under acoustics.
  8. Aug 24, 2007 #7


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    Staff: Mentor

    Not really. The vacuum of space would not carry the longitudinal acoustic sound waves at all. Any sounds will stop at the hull of the ship.

    And the answer to my quiz question, is you could use a laser from one ship and shine it on the window of the other ship, and pick up the variations in reflected signal to decode the acoustic vibrations in the other ship. Well, except that the windows in space ships are so strong and thick, that it wouldn't work as well as it does with regular windows on Earth.
  9. Aug 24, 2007 #8
    yep, I know :D:D
    that's why I said it includes E-M waves.
  10. Aug 24, 2007 #9
    but i was thinking of using celestial bodies rather than spaceships

    is that possible to establish a network all over our solar system?
  11. Aug 24, 2007 #10
    Technically, I guess it is. I'm pretty sure it would be much more economic to just use EM waves in the radio spectrum like they do now, though.

    Heh, I wasn't expecting the answer to be this sneaky.

    This idea has me fascinated. New experimental uses of active noise cancellation and evaluations of their viability sounds like a great topic. I guess this would mostly end up being a research paper rather than one that relies on self-collected experimental results. (Unless… nah, trying to build an ANC rig of any respectable quality would be a stupid idea.)

    Just a couple of follow-up questions (perhaps for those of you who have experience in the field of IB Physics):
    (a) would this approach offer enough "hard" physics to satisfy an examiner? (i.e. would I need to come up with a way of quantitavely evaluating efficiency of a particular application of noise-cancellation and how extensively would I need to use formulae to justify any claims that a certain application is or isn't viable?)
    (b) what would be a good place to look for in the way of sources? Would I have most success in a bookstore, a library or on the internet? (or perhaps scientific journals of some sort?)

    Still trying to do this on my own, of course. It's just that a little nudge in the right direction to get me started would be very helpful. ;)

    Thanks again!
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