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Last Updated: 20060821, mei

P11 - Psychoacoustics, Perception, and Listening Tests - Part 2

Friday, October 6, 2:00 pm — 5:30 pm

Chair: Brent Edwards, Starkey Laboratories - Eden Prarie, MN, USA

P11-1 Contextual Effects on Sound Quality Judgments: Part II—Multistimulus vs. Single Stimulus MethodKathryn Beresford, University of Surrey - Guildford, Surrey, UK; Natanya Ford, Harman Becker Automotive Systems - Bridgend, Wales, UK; Francis Rumsey, Slawomir Zielinski, University of Surrey - Guildford, Surrey, UK
In a previous pilot experiment (Part I; Convention Paper 6648 presented at the 120th AES Convention, Paris, France), a single stimulus method was employed to evaluate contextual effects on sound quality judgments. In this investigation (Part II) a multistimulus comparison method is used to evaluate the potential influence of listening context on sound quality judgments. Audio quality is assessed, as before, in two differing audio environments: a left-hand drive vehicle and an ITU-R BS.1116-conformant listening room. Trained and untrained listeners compared and graded audio quality for four stimuli with degradations in the midfrequency range. No identified reference (anchor) was used in the listening test, providing the opportunity for the influence of the audio environment to be observed in the results. Contraction bias, which was caused by the single stimulus method, was not evident in the results of this second study. Additionally listeners were able to discriminate between differently degraded stimuli where this was not possible in the initial research. Some small contextual effects were observed, however biases resulting from the indirect context comparison make it difficult to draw substantial conclusions.
Convention Paper 6913 (Purchase now)

P11-2 Audibility of Time Differences in Adjacent Head-Related Transfer Functions (HRTFs)Pablo Hoffmann, Henrik Møller, Aalborg University - Aalborg, Denmark
Changes in the temporal and spectral characteristics of the sound reaching the two ears are known to be of great importance for the perception of spatial sound. The smallest change that can be reliably perceived provides a measure of how accurate directional hearing is. The present paper investigates audibility of changes in the temporal characteristics of HRTFs. A listening test is conducted to measure the smallest change in the inter-aural time difference (ITD) that produces an audible difference of any nature. Results show a large inter-individual variation with a range of audibility thresholds from about 20 µs to more than 300 µs.
Convention Paper 6914 (Purchase now)

P11-3 Perceptual Evaluation of Algorithms for Blind Up-MixThomas Sporer, Fraunhofer Institute for Digital Media Technology (IDMT) - Ilmenau, Germany; Andreas Walther, Fraunhofer IIS, Technical University of Ilmenau, Ilmenau, Germany - Erlangen, Germany; Judith Liebetrau, Fraunhofer Institute for Digital Media Technology - Ilmenau, Germany; Sebastian Bube, Christian Fabris, Thomas Hohberger, Anja Köhler, Technical University Ilmenau - Ilmenau, Germany
The number of consumer home theater systems with surround capabilities has increased heavily. Nonetheless, most audio content is still two-channel stereo. Thus, to enjoy the advantages of their surround-systems for all types of content, consumers resort to systems that automatically create multichannel sound from legacy sources ("blind up-mix"). While a number of algorithms are used today, there is no commonly accepted test methodology to evaluate their sonic performance. Standardized listening test procedures evaluate audio quality relative to an unimpaired reference as a ground truth and thus are not applicable to up-mix scenarios. In this paper a new listening test procedure is described, which is designed to consistently assess the quality of up-mix (or down-mix) algorithms. First test results are presented.
Convention Paper 6915 (Purchase now)

P11-4 Pitch Transposition of Flute Tones Based on Variation of Average Spectral DistributionSean O’Leary, Niall Griffith, University of Limerick - Limerick, Ireland
The problem of pitch transposition in relation to the consistency of the timbre of a flute sound over its pitch range is investigated. The transposition method outlined here is based on the variation of the average spectral distribution with pitch, and preserving the spectral behavior in relation to the productive mechanism. A set of measures is proposed to measure the variation of the average spectral distribution with pitch, and a set of samples are analyzed over the pitch range of the instrument. These measures are used in the transposition model to correct the average spectral distribution.
Convention Paper 6916 (Purchase now)

P11-5 Pitch Coherence as a Measure of Apparent Distance in Performance Spaces and Muddiness in Sound RecordingsDavid Griesinger, Harman Specialty Group - Bedford, MA, USA
This paper demonstrates a physiological method whereby sonic distance and muddiness can be quantified through the detection of pitch fundamentals from the phase coherence of harmonics in the vocal formant range. The method allows the perceived direct/reverberant ratio of a performance or a recording to be determined from a single channel of a recording of speech or music, allowing quality assessments during actual performances. Preferred values of the direct/reverberant ratios above 1000 Hz obtained by this method are +3 to +6 dB. This result has important consequences both for performance acoustics and recording.
Convention Paper 6917 (Purchase now)

P11-6 A Comparison of Various Multichannel Loudness Measurement TechniquesAlan Seefeldt, Steve Lyman, Dolby Laboratories - San Francisco, CA, USA
In this paper two recently proposed objective measures of perceived loudness for monophonic audio signals are extended in several ways to deal with multichannel audio. The extensions range in complexity from a simple sum of the individual channels to the use of measured HRTFs to simulate the audio signals arriving at the ears. A database of subjective loudness matching data of multichannel audio is generated, and the performance of the various objective measures, including the particular multichannel measure recently adopted by the ITU-R, is compared against this data.
Convention Paper 6918 (Purchase now)

P11-7 Predicting Listener Preferences for Surround Microphone Technique through Binaural Signal Analysis of Loudspeaker-Reproduced Piano PerformancesSungyoung Kim, William Martens, McGill University - Montreal, Quebec, Canada; Atsushi Marui, McGill University - Montreal, Quebec, Canada, Tokyo National University of Fine Arts and Music, Tokyo, Japan; Kent Walker, McGill University - Montreal, Quebec, Canada
Four solo piano pieces were presented through a five-channel loudspeaker reproduction system for a pairwise preference test in a previous study, and the results of that test were described in terms of the interaction between program material and surround microphone technique. In an attempt to predict the obtained preference choices on the basis of the binaural signals recorded during loudspeaker reproduction of differing versions of these musical programs, a number of electroacoustic measures on the test stimuli were examined via stepwise multiple regression. The most successful prediction resulted from a combination of Ear Signal Incoherence (ESI) and Side Bass Ratio (SBR), regardless of methodological differences between two independently tested groups of listeners.
Convention Paper 6919 (Purchase now)

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