AES 123rd Convention - Where Audio Comes Alive
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AES New York 2007
Paper Session P1

P1 - Perception, Part 1

Friday, October 5, 9:00 am — 12:00 pm
Chair: William Martens, McGill University - Montreal, Quebec, Canada

P1-1 Room Reflections Misunderstood?Siegfried Linkwitz, Linkwitz Lab - Corte Madera, CA, USA
In a domestic living space a 2-channel monopolar and a dipolar loudspeaker system are compared for perceived differences in their reproduction of acoustic events. Both sound surprisingly similar and that is further enhanced by extending dipole behavior to frequencies above 1.4 kHz. The increased bandwidth of reflections is significant for spatial impression. Measured steady-state frequency response and measured reflection patterns differ for the two systems, while perceived sound reproduction is nearly identical in terms of timbre, phantom image placement, and sound stage width. The perceived depth in the recording is greater for the dipole loudspeaker. Auditory pattern recognition and precedence effects appear to explain these observations. Implications upon the design of loudspeakers, room treatment, and room equalization are discussed.
Convention Paper 7162 (Purchase now)

P1-2 Aspects of Reverberation Echo DensityPatty Huang, Jonathan Abel, Stanford University - Stanford, CA, USA
Echo density, and particularly its time evolution at the reverberation impulse response onset, is thought to be an important factor in the perceived time domain texture of reverberation. In this paper the psychoacoustics of reverberation echo density is explored using reverberation impulse responses synthesized via a Poisson process to have a variety of static and evolving echo densities. In addition, a recently proposed echo density measure called the normalized echo density, or NED, is explored, and related via a simple expression to echo density specified in echoes per second using echo patterns with static echo densities. A continuum of perceived time-domain texture was noted, from “sputtery” around 100 echoes per second to “smooth” above about 20,000 echoes per second, at which point it was perceptually identical to Gaussian noise. The character of the reverberation impulse response onset was explored for various rates of echo density increase, and ranged from “sputtery” for long mixing times to “instantly smooth” for short mixing times.
Convention Paper 7163 (Purchase now)

P1-3 Localization in Spatial Audio—From Wave Field Synthesis to 22.2Judith Liebetrau, Thomas Sporer, Thomas Korn, Fraunhofer IDMT - Ilmenau, Germany; Kristina Kunze, Christoph Man, Daniel Marquard, Timo Matheja, Stephan Mauer, Thomas Mayenfels, Robert Möller, Michael-Andreas Schnabel, Benjamin Slobbe, Andreas Überschär, Technical University of Ilmenau, Ilmenau, Germany
Spatial audio reproduction used to concentrate on systems with a low number of loudspeakers arranged in the horizontal plane. Wave Field Synthesis (WFS) and NHK's 22.2 two systems promise better localization and envelopment. Comparisons of 22.2 with 5.1 concerning spatial attributes on one hand, and evaluation of spatial properties of WFS on the other hand have been published in the past, but different methods have been used. In this paper a listening test method is presented that is tailored on the evaluation of localization of 3-D audio formats at different listener positions. Two experiments have been conducted. In the first experiment the localization precision of 22.2 reproduction was evaluated. In a second experiment the localization precision in the horizontal plane as a function of spatial sampling was studied.
Convention Paper 7164 (Purchase now)

P1-4 Thresholds for Discriminating Upward from Downward Trajectories for Smooth Virtual Source Motion within a Sagittal PlaneDavid H. Benson, William L. Martens, Gary P. Scavone, McGill University - Montreal, Quebec, Canada
In virtual auditory display, sound source motion is typically cued through dynamic variations in two types of localization cues: the inter-aural time delay (ITD) and binaural spectral cues. Generally, both types of cues contribute to the perception of sound source motion. For certain spatial trajectories, however, namely those lying on the surfaces of cones of confusion, ITD cues are absent, and motion must be inferred solely on the basis of spectral variation. This paper tests the effectiveness of these spectral cues in eliciting motion percepts. A virtual sound source was synthesized that traversed sections of a cone of confusion on a particular sagittal plane. The spatial extent of the source's trajectory was systematically varied to probe directional discrimination thresholds.
Convention Paper 7165 (Purchase now)

P1-5 Headphone Transparification: A Novel Method for Investigating the Externalization of Binaural SoundsAlastair Moore, Anthony Tew, University of York - York, UK; Rozenn Nicol, France Telecom R&D - Lannion, France
The only way to be certain that binaurally rendered sounds are properly externalized is to compare them to real sound sources in a discrimination experiment. However, the presence of the headphones required for the binaural rendering interfere with the real sound source. A novel technique is presented that uses small compensating signals applied to the headphones at the same time as the real source is active, such that the signals reaching the ears are the same as if the headphones were not present.
Convention Paper 7166 (Purchase now)

P1-6 On the Sound Color Properties of Wavefield Synthesis and StereoHelmut Wittek, Schoeps Mikrofone GmbH - Karlsruhe, Germany, and University of Surrey, Guildford, Surrey, UK; Francis Rumsey, University of Surrey - Guildford, Surrey, UK; Günther Theile, Institut für Rundfunktechnik - Munich, Germany
The sound color reproduction properties of wavefield synthesis are analyzed by listening tests and compared with that of stereophony. A novel technique, "OPSI," designed to avoid spatial aliasing is presented and analyzed in theory and practice. Both stereophonic phantom sources as well as OPSI sources were perceived to be less colored than was predicted by coloration predictors based on the spectral alterations of the ear signals. This leads to the hypothesis that a decoloration process exists for stereophonic reproduction as proposed in the "association model" of Theile.
Convention Paper 7167 (Purchase now)

Last Updated: 20070831, mei