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AES Barcelona 2005
Paper Session A - Spatial Perception and Processing, Part 1

Last Updated: 20050331, mei

Saturday, May 28, 09:30 — 12:00

Chair: Richard Stroud, Stroud Audio Inc. - Kokomo, IN, USA

A-1 Cues for Localization in the Horizontal PlaneJakob Jeppesen, Henrik Møller - Aalborg University, Aalborg, Denmark
Spatial localization of sound is often described as unconscious evaluation of cues given by the interaural time difference (ITD) and the spectral information of the sound that reaches the two ears. Our present knowledge suggests the hypothesis that the ITD roughly determines the cone of the perceived position (i.e., the azimuth in a polar coordinate system with left-right poles), whereas the spectral information determines the position on the cone (i.e., the elevation in the same coordinate system). This hypothesis was evaluated in a series of listening tests, where the two cues were manipulated in HRTFs used for binaural synthesis of sound in the horizontal plane. The manipulation of cues resulted in HRTFs with cues ranging from correct combinations of spectral information and ITDs to combinations with severely conflicting cues. Both the ITD and the spectral information seems to be necessary for localization in the sense that sources are localized well when the two types of cues are correct. When the cues are severely conflicting the localization performance is highly degraded.
Convention Paper 6323 (Purchase now)

A-2 Subjective Investigations of the Interaural Time Difference in the Horizontal PlaneBusson Sylvain, Nicol Rozenn, France Telecom R&D - Lannion, France; Brian Katz, Université d’Orsay - Paris, France
The Interaural Time Difference (ITD) is the primary cue for sound localization. Although ITD has been intensively studied, there are still many issues to explore. This paper focuses on the ITD in relation to minimum phase filter modeling for the binaural synthesis. Comparison between ITD extraction methods highlights discrepancies for locations near the interaural axis. A subjective experiment was carried on to know which ITD to use with a given pair of minimum phase filters. Subjects had to adjust the ITD of a test sound in order to move it as close as possible to a target sound. The psychoacoustic value of the ITD is compared with computational estimates from the Head Related Transfert Function (HRTF).
Convention Paper 6324 (Purchase now)

A-3 Localization and Image Size Effects for Low Frequency SoundAlan Subkey, Bassett Acoustics - Braddon, Australia, and The University of Sydney, Sydney, Australia; Densil Cabrera, The University of Sydney - Sydney, Australia; Sam Ferguson, The University of Sydney - Sydney, Australia
Using four subwoofers, this study investigates horizontal auditory image characteristics for one-third octave bands of pink noise in the frequency range 25 Hz to 100 Hz. The subwoofers were located at 90-degree intervals: 45 degrees to the left and right, and in front of and behind the subject. Single noise bands, coherent pairs, and incoherent pairs were subjectively assessed. Subjects drew the auditory image as an ellipse on a response sheet. Results indicate that left-right discrimination occurs even at the lowest frequencies of human hearing—a finding consistent with other recent research. Image width and depth are correlated, increasing at low frequencies for the stimuli tested and for simultaneous presentation of coherent or incoherent signals. Like other recently published studies using multiple channels of low frequency sound, this paper indicates that multiple subwoofers should be beneficial in multichannel loudspeaker systems.
Convention Paper 6325 (Purchase now)

A-4 Audibility of Time Switching in Dynamic Binaural SynthesisPablo Faundez Hoffmann, Henrik Møller, Aalborg University - Aalborg, Denmark
In binaural synthesis, signals are convolved with head-related transfer functions (HRTFs). In dynamic systems, the update is often done by cross-fading between signals that have been filtered in parallel with two HRTFs. An alternative to cross-fading that is attractive in terms of computing power is direct switching between HRTFs that are close enough in space to provide an adequate auralization of moving sound. However, direct switching between HRTFs does not only move the sound but may also generate artifacts such as audible clicks. HRTF switching involves switching of spectral characteristics and timing characteristics (ITD), and the audibility of these were studied separately. The first results, data on minimum audible time switch, MATS, are presented.
Convention Paper 6326 (Purchase now)

A-5 Interpolation of Head Related Transfer Functions Considering AcousticsThibaut Ajdler, Christof Faller, Luciano Sbaiz, Ecole Polytechnique Federale de Lausanne - Lausanne, Switzerland; Martin Vetterli, Ecole Polytechnique Federale de Lausanne - Lausanne, Switzerland, and University of California, Berkley, CA, USA
We are proposing an interpolation technique for head related transfer functions (HRTFs). To derive the algorithm we study the dual problem where sound is emitted from the listener's ear and the generated soundfield is recorded along a circular array of microphones around the listener. The proposed interpolation algorithm is based on the observation that spatial bandwidth of the measured sound along the circular array is limited (for all practical purposes). Further, we observe that this spatial bandwidth increases linearly with the frequency of the emitted sound. The result of the analysis leads to the conclusion that the necessary angle between consecutive HRTFs is about 5 degrees in order to be able to reconstruct all HRTFs at 44.1 kHz temporal sampling frequency in the horizontal plane.
Convention Paper 6327 (Purchase now)

©2005 Audio Engineering Society, Inc.