MacBook sound when dropped.

Discussion in 'Mac Basics and Help' started by HckySo, Jun 25, 2006.

  1. HckySo macrumors 6502

    HckySo

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    #1
    I'm new to the MacBook, obviously as everyone is. I dropped it on my couch from about a foot above when I tripped over my stupid cat. Anyway when it fell I could hear my MacBook make this high pitch noise when it was falling so I took it and kind of dropped it in my hands and it made the noise again. Is that my MacBook detecting when it's falling? I remember hearing somewhere that it detects when it is falling and stops the pin on the HD so no data is damaged. Could that be what I'm hearing?
     
  2. HckySo thread starter macrumors 6502

    HckySo

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    #3
    But he's so cute!

    ....and he just threw up on hard wood floor! GET OUT!
     
  3. netdog macrumors 603

    netdog

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    #4
    I can't understand why iGary might have the kind of karma that would attract faulty hardware. :p
     
  4. iGary Guest

    iGary

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    #5
    Ha!

    Well I don't plan on dropping my PB to find out if that noise you experienced was the sudden motion sensor, but maybe someone else has had the experience. :)
     
  5. someguy macrumors 68020

    someguy

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    #6
    I don't know if the SMS detects falling so much as the impact thereafter, though it might be programmed to begin parking the heads and whatnot when it foresees an impact (i.e. falling, being swung. etc) so that the disk will be stopped before it's too late.

    Anyone know for sure?
     
  6. mkrishnan Moderator emeritus

    mkrishnan

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    #7
    SMS uses a very small accelerometer. It detects acceleration. If you drop your notebook, it accelerates at 9.8 m/s^2 until it reaches terminal velocity (if it falls far enough). And then obviously accelerates rapidly in the other direction when it hits something.

    But anyway, SMS looks for the falling acceleration -- not the impact acceleration. By impact, it's too late. That's why it kicks in if you take your laptop and simulate falling in your hands by jerking it down. When it detects that initial acceleration due to falling, it parks the hard drive to prevent damage.

    :)
     
  7. someguy macrumors 68020

    someguy

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    #8
    I see, looks like I had it backwards then! :)
     
  8. netdog macrumors 603

    netdog

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    #9
    You do plan on killing the cat though. :D
     
  9. mmmcheese macrumors 6502a

    mmmcheese

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    #10
    And what is the terminal velocity of a notebook? Who wants to figure it out? Haha.
     
  10. CanadaRAM macrumors G5

    CanadaRAM

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    #11
    Just a bit faster than the terminal velocity of a cat.
    More aerodynamic.

    (BTW, the cat also makes screeching sounds when dropped a distance. Beware, though, when testing, because cats have a sophisticated pre-Sudden Motion Sensor system that deploys claws pro-actively to prevent the fall in the first place. Then, the screeching noise will be coming from you.)
     
  11. mkrishnan Moderator emeritus

    mkrishnan

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    #12
    :)

    The accelerometer is a micro electro-mechanical system (MEMS). If I remember correctly, a typical design is to have a very small cantilevered beam (like a diving board in a pool) that is suspended just above another conductive surface by a very small distance. If there is a voltage on this beam / arm, then the potential on the other side is very dependent on the distance between beam and the surface. The beam distorts during acceleration, changing the distance and the signal on the other side. And so the acceleration can be read. If you have three such beams in three different orientations, you can read any acceleration. :) Another design is to have a body that is connected to a ring on two sides by little bars -- the bars twist and you can measure this.

    Anyway, they're very sensitive. The accelerometer in the Macs can read signals much, much smaller than the acceleration of falling. That's how the little hacks, like the thing that lets you play a game by tilting the computer, or SmackBook Pro work. :)
     
  12. CanadaRAM macrumors G5

    CanadaRAM

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    #13
    In any case:
    It's a VBI™ to move a hard drive while it is operating.
     

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