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Multidirectional audio decoding

  • US 6,449,368 B1
  • Filed: 03/14/1997
  • Issued: 09/10/2002
  • Est. Priority Date: 03/14/1997
  • Status: Expired due to Term
First Claim
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1. A 2×

  • 2 port audio crosstalk-cancelling network for mapping two audio source channels, each having an associated source direction, to two audio presentation channels, each adapted for application to a respective one of a pair of transducers, each transducer having a position relative to the source directions, wherein the cross-talk cancelling network implements a matrix C of dimension 2×

    2 in which each of the matrix elements is a frequency-domain transfer function and said matrix C is the inverse of a room matrix R in which each of the matrix elements is also a frequency-domain transfer function, the matrix R representing a 2×

    2 port network for mapping two transducer positions to two listening positions. the left ear and the right ear of a listener, the network comprisinga first signal combiner and a second signal combiner, each signal combiner having at least two inputs and an output, wherein one of said source channels is coupled to an input of said first signal combiner and another of said source channels is coupled to an input of said second signal combiner, and one of said audio presentation channels is coupled to the output of said first signal combiner and another of said audio presentation channels is coupled to the output of said second signal combiner, and two signal feedback paths, a first signal feedback path and a second signal feedback path, each feedback path having a time delay and frequency dependent characteristic, and each feedback path having an input and an output, wherein the input of said first signal feedback path is coupled to the output of said first signal combiner and the output of said first signal feedback path is coupled to the other input of said second signal combiner, the input of said second signal feedback path is coupled to the output of said second signal combiner and the output of said second signal feedback path is coupled to the other input of said first signal combiner, each of said feedback paths has a time delay representing the additional time for sound to propagate along the acoustic path between a transducer and the listener'"'"'s ear farthest from said transducer with respect to the time for sound to propagate along the acoustic path between the same transducer and the listeners ear closest to said same transducer, and each of said feedback paths has a frequency dependent characteristic representing the smoothed difference in the attenuation in the acoustic path between a transducer and the listener'"'"'s ear farthest from said transducer and the attenuation in the acoustic path between the same transducer and the listener'"'"'s ear closest to said same transducer, wherein said smoothed difference in the attenuation is implemented by one or more simple digital filters requiring low processing power, said signal combiners, signal feedback paths, and couplings therebetween having polarity characteristics such that signals processed by a feedback path arc subtractively combined with signals coupled to the other input of the respective signal combiner, fixed amplitude level attenuators in each of the network'"'"'s inputs, and variable amplitude level boosters in each of the network'"'"'s outputs, the boosters each including a scaler for scaling the boost between a level which restores the input attenuation and an attenuated level which avoids clipping in the output signal.

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