Why do we need surround sound if we only have 2 ears?

Discussion in 'Speakers & Subwoofers' started by trey-m, Mar 16, 2005.

  1. trey-m

    trey-m Stunt Coordinator

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    This may be more of a physiological question rather than a technological one: How do our ears determine (front/back) direction of a sound source? Without too much thought, I'm thinking that sounds originating from in front of us have larger amplitudes at higher frequencies than those that come from behind us (because our earlobes block the high frequency sounds). But if this is true, doesn't that mean any sound could be simulated as originating from behind us by altering the frequency spectrum? Could this possibly translate to not ever theoretically needing more than 2 speakers?
     
  2. Ilkka R

    Ilkka R Second Unit

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    Direction is sensed by the phase difference between our ears. That's why we can't localize low sounds (long waves).

    But on the other hand, if sound is coming directly in front or back of us, there is no phase difference. I checked my old physics books and they say that the head (skull) causes attenuation and also the shape of the earlobes helps sensing the direction of sound. Also reflections and turning your head a little bit helps.

    I would think that in an anechoic chamber it would be extremely difficult to sence the direction of the sound.
     
  3. John Garcia

    John Garcia Executive Producer

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    You don't just hear direct sound, you hear reflected sound as well, so your ears aren't blocking everything. Even with one ear, you would be able to tell if something was in front, back, left or right of you.

    Each speaker is playing a different sound to create the simulated environment's spatial cues.
     
  4. trey-m

    trey-m Stunt Coordinator

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    I agree that reflections also play a large part in sensing direction of sound. But couldn't those too be simulated? For example, imagine a human shaped dummy with 2 "perfect" microphones in the location of the ears. Now play a movie in surround sound and record it with the stereo mics. In theory, wouldn't listening to this recording using "perfect" stereo headphones achieve the exact same surround sound as if you were sitting in the room for the original playback? Thus a "perfect" recording and "perfect" headphones are all we need?
     
  5. Rokzi

    Rokzi Stunt Coordinator

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    Doesn't Sony already have "Surround" headphones?
    Also, my panasonic DVD player has VSS (Virtual Surround Sound) which allows you to hear a (you guessed right!) simulated surround sound when all that you have are stereo speakers (either your TV's stereo speakers or your stereo-only recevier setup).

    I guess what you are asking about is "Simulated" Surround Sound. If so, then isn't that technology already been out for quite a while?
     
  6. Ilkka R

    Ilkka R Second Unit

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    Haven't you guys ever heard of A3D/EAX4/DolbyHP or similar? They can make a virtual soundstage using only headphones. Is it perfect? No.
     
  7. Rokzi

    Rokzi Stunt Coordinator

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    Could be because they are simulated and not real surround.
     
  8. Mike LaBorde

    Mike LaBorde Auditioning

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    The technique of recording with microphone placed in dummy ears in a dummy head has been around for at least 50 years. It is usually referred to as binaural recording. It has several problems though. It works only played back through earphones since it must deliver the two "ears'" sound to your ears exactly without introducing any reflections. You also still get the sound in the center of your head effect with any sound that is directly in front of or in back. You will get varying degrees of success in hearing sounds moving around your head if they are meant to be directly in front or behind.

    There have been several attempts to produce loudspeakers that would play back binaural records but none have been successful, to my knowledge.

    There used to be a number of binaural recording demos floating around. I have a few on LP and there was at least one dramatization of a Stephen King story recorded for radio and played binaurally. I suggest that anyone really interested do a Google (or your favorite search engine) search.
     
  9. John Garcia

    John Garcia Executive Producer

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    It's already been done years ago (*edit binaural was it!), though I think the use in any major music releases has already stopped. The mic was basically a human shaped head with special mics in the ear positions. The recordings do have a cool spatial feel to them, but it's still not the same as discrete sounds spread through the room. There's a good example on T2:Ultimate Editioin and I believe also on the Extreme Edition. I own one CD that is binaural.

    With a VERY good recording, you can retrieve quite a bit of the spatial information that can be played back with just two speakers, with no surround processing at all, but two speakers will not fill the room the same way as multiple speakers. Examples of recordings would be any of the Patricia Barber SACDs (MoFi). They are nothing short of amazing.
     
  10. Ilkka R

    Ilkka R Second Unit

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    Also speakers used do have a huge effect. Panel or electrostatic speakers e.g. Maggies or Martin-Logans have a very good soundstage.

    And I double that Patricia Barber, try Verse for example.
     
  11. Robert_Dufresne

    Robert_Dufresne Stunt Coordinator

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    There is an audiophile recording company (Fidelio) here in Québec that uses two specially designed microphones spaced about six inches apart to do there recordings. They take there setup to churches jazz clubs etc. . The results are pretty good.
     

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