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Panning and Psychoacoustics

Discussion in 'Recording' started by MindMeld, Dec 20, 2002.

  1. MindMeld

    MindMeld Guest

    I was thinking today about stereo--- and a paper that i wrote a while back.

    If i was listning to a single point source, and i moved to the left or right of it, not only would there be an amplitude difference, but there would be a time difference as well. So if a source was to the right of me, my left ear would recieve the information slightly later then the right ear.

    Now when we are panning stuff around in studio applications, we only effect the amplitude of the signal between the left and right speakers. What we need to also do is to add a delay the the far speaker that increases the more hard panned the signal becomes.

    This will only work with mono sources.. I'm not sure how to work with stereo sources.
    Your thoughts?
    Marsh
     
  2. Kurt Foster

    Kurt Foster Distinguished Member

    If you take a mono signal, split it, running one through a short (10 - 20 ms for example) delay. Pan the delayed signal to one side and the dry signal to the other side at exactly the same dB level, you will perceive the dry (un - delayed) sound as the loudest. Psycho acoustic effect. The human ear will always perceive the first sound as loudest. Every time. I discovered this many years ago (I'm too old!) when I worked primarily on 4 track and was looking for ways to "stereoize" my mixs. Later research and reading confirmed my first impressions. Try this and watch the meters. Try to make a mono signal sound stereo. You will find yourself bringing up the delayed signal a couple of dB's louder on one side of the meters to make it sound like it's in the middle
    Fats
    ---------------------------------------------------------------------------------------------------
    It's my opinion, I'll play with it if I want to!
     
  3. Mario-C.

    Mario-C. Active Member

    is this the Haas effect you guys are talking about ?
     
  4. Kurt Foster

    Kurt Foster Distinguished Member

    Mario,
    Yes, it is. I would have said that if I had remembered it, so I could really sound like I knew what I was talking about! :D ............ Fats
     
  5. MindMeld

    MindMeld Guest

    Cedar, i've used this trick before on multiple occasions to "stereoize" a track. And i guess its on the same vein as what i'm asking about. Its just more a question of smaller increments 1-2 milliseconds. stuff that we can't perceive directly, but unconciously we know is more realistic. I guess you could do this in the DAW, but you would have to ask what is the distance from the source and stuff like that
     
  6. Kurt Foster

    Kurt Foster Distinguished Member

    Marshall,
    I personally like mono on some things., Using short delays as you described can cause phase anomalies and cancellation. These days with DAW I no longer have to deal with a shortage of tracks so the things I want in stereo, I record in stereo. Panning a mono signal to one side while panning another to the other side does not make stereo. Stereo is a combination of sum and difference signal. There is thread in which we have motioned Alan D. Blumlein and I posted a really cool link but I'll post one again here in regards to this topic.
    http://www.doramusic.com/

    This is a book by Robert Charles Alexander and it has some really cool excerpts from a book about Blumleins life and work, some which mention the theory regarding sum and difference. Check it out. Read the text and click on "Chapter Three". What I could understand was fascinating! This is just a small sample of the excerpts on the link.

    "In a series of surviving hand-written notes dated 25 September 1931, Blumlein heads the page "Binaural Speech Trials", though there is no direct evidence that any such trials were carried out at this time. Blumlein calculates the value of an element he calls 'K', which is the ability to modify the signal of the microphones to recreate the phase difference at the listeners ears. The path difference from the two loudspeakers can give sufficient phase difference when they are summed in the listeners ears, if the difference in amplitude of the signals is then correctly modified. This Blumlein does by deriving the 'sum' and 'difference' signals, the difference signal being fed through p/2 using a current fed capacitor which also reduces the signal by 6dB per octave (6dB/8ve). This new difference signal is then added to and subtracted from the sum signal to form two new signals to the loudspeakers. Blumlein called the process 'Shuffling' (which we take today to have a different meaning to that which Blumlein originally uses here)"
    …. Robert Charles Alexander
    This does wander a little off topic but I thought it was very cool stuff! ………………… Fats
    ---------------------------------------------------------------------------------------------------
    It's my opinion, I'll play with it if I want to!
     
  7. John Sayers

    John Sayers Active Member

    It will only sound like it's in the middle if the delay is LESS than 18msec. Once the delay increases past 18msec the ear splits in into two separate sounds left and right.

    cheerts
    john
     
  8. Kurt Foster

    Kurt Foster Distinguished Member

    John,
    That's what I said, 10 - 20 ms. Toodles, Fats
     
  9. realdynamix

    realdynamix Well-Known Member

    I have 5 delays in my little rack for that very reason, they don't have to be expensive, but must be able to dial in the very short delay needed.
    I got this idea from a Ted Nuggent tune off FM. The station (for some reason) didn't use it's stereo coupler on it's main compressor/limiter, WOW! A whole lotta stereo, but while Ted was rippin' some licks on the left it naturally came forward in the mix yet still maintained a stereo image, and when back to the verse, it regained it's position in the mix. In other words, try NOT using a coupler if and when limiting the special and desired stereo track.
    --Rick
     
  10. realdynamix

    realdynamix Well-Known Member

    :d: Ooooppps Forgot, Marshall, the delay technique you describe is the fundimental basis for most commercially produced spatial enhancers.

    Happy Holidays all!
    --Rick
     
  11. Kurt Foster

    Kurt Foster Distinguished Member

    As I understand it, BBE enhancers work by realigning frequencies by delaying low frequencies through use of a crossover network then summing lows and highs, allowing the highs to form the leading edge of the transient. In the case of the Aphex enhancers it is much the same process but a miniscule amount of distortion is also added. While this is a delay technique it is not the same thing. th' Fat bastard :tu:
     

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