2:00 pm

J-1 Design, Generation, and Analysis of Digital Test Signals

Frantisek Kadlec, Czech Technical University, Prague, Czech Republic

Design and generation of test signals for measurement of electroacoustic systems, as well as for psychoacoustic testing is discussed. The main focus is on a digital generation of low-level harmonic test signals and an observation how subsequent DSP processing of those introduces a distortion. Mathematical analysis describes the origin of this distortion, and its audible perception is also examined. Further it is shown how the influence of various distorting components on audible perception can be minimized by using dither. Additionally, the generation of sweeping frequency signals and multitone signals is discussed.

Convention Paper 5453

2:30 pm

J-2 Interactions between Surround Sound Level and the Immersive Feeling in the Multichannel Movie Experience

Thibaud Guichardan, Consultant, Aix les Bains, France

With the increasing availability of surround sound in cinemas, home theatres and multimedia computers, the demand for surround sound programs is constantly rising. Still, it remains difficult to assess to which extent does the use of surround sound increase the feeling of immersion in the total movie-viewing experience. The purpose of this study is to attempt an evaluation of the variation of the viewer's immersive sensation, with the change of the surround sound proportion, also taking into account the scenes dramatic content.

Convention Paper 5454

3:00 pm

J-3 Descriptive Analysis of Speech Quality in Mobile Communications: Descriptive Language Development and External Preference Mapping

Ville-Veikko Mattila, Nokia Research Center, Tampere, Finland

Perceptual analysis of speech quality in mobile communications was carried out by semantic differentiation and external preference mapping, and the developed at tributes were mapped to overall quality judgements. A clean speech sample and a speech sample corrupted by car cabin noise from two speakers were processed by different processing chains representing, e.g., transmission of speech over real GSM networks, various standardised speech coders and speech coding with erroneous transmission channels, etc., resulting in a total of 170 samples. The perceptual characteristics of the test samples were described by 18 screened and trained subjects. The final descriptive language with 21 attributes and their rating scales were developed in panel discussions. The scaled attributes were mapped to overall quality evaluations collected from 30 screened and trained subjects by partial least-squares regression (PLSR).

Convention Paper 5455

3:30 pm

J-4 The Effect of Loudspeaker Type on the Identification of Vowel-Like Harmonic Complexes

Sheila Flanagan and Brian C. J. Moore, University of Cambridge, Cambridge, Cambridgeshire, UK

Listeners were required to identify which of six vowel-like harmonic complexes was presented on each trial. The components of the complexes were added either in cosine or in random phase and the fundamental frequency was 50 or 100 Hz. The sounds were reproduced in a typical listening room via a distributed mode loudspeaker (DML) or a conventional loudspeaker. Overall accuracy of vowel identification was similar for the two loudspeakers. For both loudspeakers, performance was better for cosine phase than for random phase, indicating that phase information is preserved to some extent even in the far field.

Convention Paper 5456

4:00 pm

J-5 An Investigation of Interaural Time Difference Fluctuations, Part 3: The Subjective Spatial Effect of Fluctuations in Continuous Stimuli Delivered Over Loudspeakers

Russell Mason, Francis Rumsey and Bart de Bruyn, University of Surrey, Guildford, Surrey, UK

The subjective spatial effect of continuous noise signals with interaural time difference fluctuations was investigated. These fluctuations were created by sinusoidal interchannel time difference fluctuations between signals that were presented over loudspeakers. Both verbal and non-verbal elicitation techniques were applied to examine the subjective effect. It was found that the predominant effect of increasing the fluctuation magnitude was an increase in the apparent width of the perceived sound source.

Convention Paper 5457

4:30 pm

J-6 An Investigation of Interaural Time Difference Fluctuations, Part 4: The Subjective Effect of Fluctuations in Decaying Stimuli Delivered Over Loudspeakers

Russell Mason, Francis Rumsey and Bart de Bruyn, University of Surrey, Guildford, Surrey, UK

The subjective spatial effect of decaying noise signals with interaural time difference fluctuations was investigated. These fluctuations were created by sinusoidal interchannel time difference fluctuations between signals which were presented over loudspeakers. Both verbal and non-verbal elicitation techniques were applied to examine the subjective effect. It was found that the predominant effect of increasing the fluctuation magnitude was an increase in the apparent width of the acoustical environment whilst the apparent size of the perceived sound source did not change.

Convention Paper 5458