How does QSound work?

Discussion in 'Archived Threads 2001-2004' started by Colin Dunn, Feb 9, 2002.

  1. Colin Dunn

    Colin Dunn Supporting Actor

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    RicP's thread about the Nickelback CD in the music area brings up a question. I have read in many places that the QSound process can create the illusion of "surround sound" from a traditional 2-channel stereo system. Something about "tricks with the phase" of the audio signal supposedly yields this effect.

    But how can playing with the phase of an audio signal give the illusion of sound outside the confines of the speakers, or even behind you, when you only have two speakers (left & right) in front of you?

    It's a mystery to me...
     
  2. Mark Hayenga

    Mark Hayenga Supporting Actor

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    It is extremely complicated, and I believe it relates to head related transfer functions (HRTFs). Basically, they figure out what a signal behind you, to the left of you, to the right of you, etc. "looks like" at your ear (looks like signal-wise I mean), and then manipulate the music signal to emulate those effects. With the technique you can get much more than just wide soundfields, I had a prof who was really into this stuff as a hobby and had read journal articles on this being applied to vertical sounds and sounds from behind you. I've got two discs encoded with Qsound I can bring to the next HTF meet if you're interested.
     
  3. Mark Hayenga

    Mark Hayenga Supporting Actor

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    You might try google searching on HRTFs. Be aware that this is really senior and graduate level engineering acoustic type stuff, you may want to familiarize yourself with basic ideas of impulse response, frequency response, convolution, etc. to get the most out of surfing the sites that are likely to come up. This is a really neat field of study. Here's some of the stuff I pulled up in my brief searching:
    http://interface.cipic.ucdavis.edu/C...TF/3D_HRTF.htm
    http://nsf-workshop.engr.ucf.edu/papers/Algazi.asp
     
  4. Colin Dunn

    Colin Dunn Supporting Actor

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    Mark -

    Thanks for the links. It's beyond my level of knowledge about acoustics/engineering, but gives me somewhat of an idea of what can be done in a recording studio to manipulate sound of a two-channel recording.

    Could you bring those CDs to the next Austin meet?
     

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