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Last Updated: 20060821, mei

P19 - Multichannel Sound

Sunday, October 8, 9:00 am — 11:30 am

Chair: Nicolas Saint-Arnaud, Dolby Laboratories - San Francisco, CA, USA

P19-1 High-Frequency Interpolation for Motion-Tracked Binaural SoundRoger Hom, Intel Corp. - Folsom, CA, USA; V. Ralph Algazi, Richard Duda, University of California at Davis - Davis, CA, USA
Motion-tracked binaural (MTB) recording captures and exploits localization cues resulting from head rotation. The pressure field around the recording head is sampled with several microphones, and a head tracker on the listener’s head is used to interpolate between the microphone signals. Although time-domain interpolation works at low frequencies, phase interference causes problems at high frequencies. We previously reported on a simple procedure whereby low-frequency components were continuously interpolated, but high-frequency components were obtained from the microphone nearest to the listener’s ear. Although effective, this technique may result in audible switching artifacts. In this paper we present and evaluate methods for continuous high-frequency interpolation of the spectral magnitudes of adjacent microphones that essentially eliminate spectral discontinuities arising from head rotation.
Convention Paper 6963 (Purchase now)

P19-2 Perceptual Importance of Karhunen-Lòeve Transformed Multichannel Audio SignalsLars Henning, Yu Jiao, Slawomir Zielinski, Francis Rumsey, University of Surrey - Guildford, Surrey, UK
The Karhunen-Lòeve Transform (KLT) can be used to reduce the interchannel redundancy of multichannel audio signals. For this paper the perceptual importance of Karhunen-Lòeve transformed multichannel audio signals was systematically studied using two experiments. The first experiment investigated the perceptual effects caused by removing some KLT eigenchannels. The results showed that some eigenchannels are not perceptually important and consequently can be discarded with minimal degradation of basic audio quality. The second experiment involved further investigation on the perceptual effect of KLT processing on the audio quality of multichannel audio as a function of the nature of the multichannel audio and eigenvalue extraction methods of KLT processing. It was also attempted to establish the relationship between the order of perceptual importance and the order of statistical importance of KLT eigenchannels.
Convention Paper 6964 (Purchase now)

P19-3 A New Upmixer for Enhancement of Reverberance Imagery in Multichannel Loudspeaker Audio ScenesJohn Usher, McGill University - Montreal, Quebec, Canada
This paper introduces a new signal processing system which enhances reverberance imagery (i.e., perceived ambiance or listener envelopment) in multichannel loudspeaker audio scenes. Sound components that affect reverberance imagery are extracted from a pair of unencoded audio signals and are radiated with two additional loudspeakers behind the listener. The new “ambiance extraction” system improves upon all extant systems by using a novel automatic (blind) equalizer based on the normalized least means square (NLMS) algorithm to align the input signals with respect to both level and phase in order to create the difference signal. The alignment is typically undertaken using a 1024-tap frequency and ±10 ms time equalizer, which allows sound components with a high short-term correlation to be removed from the input audio signals. Subjective and objective evaluation was undertaken with recordings of solo musical performances in a concert hall, and show that the new system provides a new, computationally practical, high-quality solution to the problem of ambiance extraction for audio upmixing.
Convention Paper 6965 (Purchase now)

P19-4 Natural Reproduction of a Symphony Orchestra by the Advanced Multichannel Live Sound SystemKimio Hamasaki, Toshiyuki Nishiguchi, Hiroyuki Okubo, Yasushige Nakayama, Reiko Okumura, Masakazu Iwaki, NHK Science & Technical Research Laboratories - Tokyo, Japan
An advanced multichannel audio system for reproducing a live sound field with an ultimate sensation of presence and reality was set up and studied. The goal of this system is to provide listeners with a natural reproduction of orchestral music, as if they were hearing it in an actual sound field such as that in a concert hall. Subjective evaluations of hearing impression on orchestral sound were carried out to determine which attributes of a front sound stage were necessary for the natural reproduction of an orchestra. The results of the evaluations showed that perceptions of width, depth, and localization of the orchestral sound influence the impressions of presence and reality.
Convention Paper 6966 (Purchase now)

P19-5 Localization in Horizontal-Only Ambisonic SystemsEric Benjamin, Dolby Laboratories - San Francisco, CA, USA; Richard Lee, Consultant - Cooktown, Queensland, Australia; Aaron Heller, SRI International - Menlo Park, CA, USA
Ambisonic reproduction systems are unique in their ability to separately reproduce the pressure and velocity components of the recorded audio signals. Gerzon proposed a theory of localization in which the human auditory system is presumed to localize using the direction of the velocity vector in the reproduced sound at low frequencies and the energy vector at high frequencies. An Ambisonic decoder has the energy and velocity vectors coincident. These are the directions of the apparent source when the listener can turn to face it. Separately maximizing the low-frequency and mid/high-frequency operation of the reproduction system can optimize localization where the listener cannot turn to face the apparent source. We test the localization of horizontal-only Ambisonic reproduction systems using various narrow-band test signals to separately evaluate low-frequency and mid-frequency localization.
Convention Paper 6967 (Purchase now)

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