v3.1, 20040423, ME

Session Z5 Sunday, May 9 16:00 h–17:30 h
Posters: Psychoacoustics, Perception, and Listening Tests

Z5-1 The Causal Relationship of Headphone Tone-Coloration Variations Related to the Human Pinna Influence—Florian M. König, Ultrasone AG, Penzberg, Germany
Head-related sound reproduction devices vary in transducer characteristics: the basic acoustic principles such as open/closed or circum- or supra-aural systems. Furthermore, the transducers de-centered placement inside the ear cup influences the tone quality. These headphone techniques were evaluated many times. One creation with a spatial reproduction of sound was much more conspicuous statistically because of a higher quantity recommended sound quality judgment as “too much” and “less high frequency range.” This forced investigations to find the reason for those strange review accumulations. Four different headphone types were measured by seven testers by inserting probe microphones in the auditory canal. The research result shows an electro-acoustic cause for perceived tone coloration of headphones by transducer positioning and the human pinna filtering efficiency.
Z5-2 Auditory Cues in the Perception of Self-Motion—Bill Kapralos, Daniel Zikovitz, Michael Jenkin, Laurence R. Harris, York University, Toronto, Canada and Centre for Research in Space Technology, Toronto, Ontario, Canada
Despite its potential importance, few studies have methodically examined the role of auditory cues in the perception of self-motion. Here we describe a series of experiments that investigate the relative roles of various combinations of physical motion and decreasing sound source intensity cues to the perception of linear self-motion. Subjects were blindfolded and physically moved toward a target in the presence or absence of a fixed-intensity stationary sound source, remained stationary while presented with a sound stimulus whose intensity was decreased or remained stationary while the sound stimulus was physically moved away from them. In all conditions an over-estimation of self-motion resulted that systematically varied with acceleration. Performance was most veridical with both auditory and physical cues. Without physical motion, auditory cues resulted in the greatest over-estimation, however, accuracy improved with increasing acceleration.
Z5-3 A New Mathematical Approach to Describe Localization—Philip Mackensen, T-Systems, Berlin, Germany
The localization of a single sound source can be described mathematically by a new formalism to be presented here. Commonly, the HRTF (head-related transfer function) is described as a function of variables related to the sound source position and of variables related to the spectrum. In this new approach the multivariable representation of the HRTF is replaced by introducing two independent transfer functions, one only regarding the position and the other regarding solely the source’s spectral attributes. Therefore, it can be separated between the three dimensional local space and the “spectral space.” This offers a localization independent of the Gestalt of the sound source.
Z5-4 Strategies to Increase the Applicability of Methods for Objective Assessment of Audio Quality—Jayme Garcia Arnal Barbedo, Amauri Lopes, State University of Campinas, Campinas, Brazil
The current ITU standard for objective assessment of audio quality, Perceptual Evaluation of Audio Quality (PEAQ), has some shortcomings that prevent its reliable use for a number of codification conditions and some kinds of signals. This paper aims to improve the PEAQ performance through the following proposals: (1) modifications in the manner the signals are submitted for the assessment; (2) improvement of existing Model Output Variables (MOVs); (3) creation of new MOVs; (4) determination of a better architecture for the neural network that maps the MOVs into a single estimate for the subjective score. The results are compared to those ones achieved by PEAQ.
Z5-5 Subjective Evaluation of an Equalization Method for Loudspeakers Based on Random Parametric Optimization of IIR Filters—Germán Ramos, José Javier López, Universidad Politecnica de Valencia, Valencia, Spain
In this paper a subjective evaluation of a novel method for loudspeaker equalization is presented. The equalization is performed using a direct method with random parametric optimization for the design of a bank of second-order peak filters, RaPOSOS. The subjective evaluation has been carried out using a preselected jury composed of lecturers, research staff, and university students related to the audio engineering field. For evaluating its performance, it has been compared with other well known equalization methods using the ABX test. In particular, our method with different levels of approximation, has been compared with long FIR filters obtained by minimum square error criteria. The results show that with relatively low-order filters, the perceived difference is anecdotic or nonexistent, requiring less computational cost.
Z5-6 A Composite Physiological Model of the Inner Ear for Audio Coding—Alexei V. Ivanov¹, Alexander A. Petrovsky^2
1 Belorussian State University of Informatics and Radioelectronics, Minsk, Belarus
² Bialystok Technical University, Bialystok, Poland
The alternative approach to psychoacoustical masking modeling is to model such phenomena as suppression, spread-of-excitation, and IHC adaptation, which are among the underlying physiological phenomena for psychoacoustically observed masking. This paper proposes a physiologically grounded model for threshold estimation. It includes a reconfigurable nonuniform filterbank to simulate the “cochlear amplifier” and associated suppression effect; a digital compartmental IHC model to account for their adaptive responses; a spiking neuron auditory nerve model to simulate the spread-of-excitation. It allows designing coders, which retain enough information to create the identical excitation pattern in the auditory nerve compared to that of the original signal. Since our model is based on the masking physiology, its application is justified in the complex audio signals case.
Z5-7 Perception of Temporal Decay of Low-Frequency Room Modes —Matti Karjalainen¹, Poju Antsalo¹, Aki Mäkivirta², Vesa Välimäki^1
1 Helsinki University of Technology, Espoo, Finland
² Genelec Oy, Iisalmi, Finland
Modal equalization has recently been of research interest in order to improve sound reproduction in rooms that have excessively strong modes at low frequencies. Instead of acoustic treatment by expensive and space-reserving absorbing structures, modal equalization is based on DSP affecting the electric-to-acoustic reproduction chain. Several DSP-based techniques for modal equalization have been proposed recently and tested in performance. From a perceptual point of view, however, no clear picture of the importance of controlled temporal decay has been shown, although it is known that toward lowest frequencies human hearing becomes increasingly insensitive to temporal details. In the present paper we conducted listening tests where only a single synthetic mode with increased decay time but magnitude-equalized response was used to find the JND threshold of increased decay time. The main conclusion is that at typical listening levels, downward to 100 Hz, the modal decay time (T₆₀) is allowed to increase from 0.3 seconds by 0.1 to 0.4 seconds, while at 50 Hz even decay times of up to 2 seconds do not make a noticeable difference.
Z5-8 Psychoacoustic Cues in Room-Size Perception—Sharaf Hameed, Jyri Pakarinen, Kari Valde, Ville Pulkki, Helsinki University of Technology, Espoo, Finland
The ability of human listeners to estimate the size of a room from the acoustical response of that room is an interesting and not yet thoroughly examined phenomenon. This paper uses simulated multichannel room impulse responses convolved with speech signals as stimuli in listening tests to explore the perception of room size. The synthetic room impulse responses contained two adjustable parameters, and our goal was to study how these parameters affect the perceived size of this virtual room. Listening tests were conducted to test the effect of reverberation time and the direct to reverberant energy ratio (D/R ratio). Sound samples with different parameter settings were presented as stimuli in a paired comparison test procedure. The results reveal that reverberation time is unequivocally the most important parameter. It appears that D/R ratio is not used in room size perception.
Z5-9 Proposed Changes to the Methods of Objective, Perceptual -Based Evaluation of Compressed Speech and Audio Signals—Piotr Kozlowski, Andrzej Dobrucki, Wroclaw University of Technology, Wroclaw, Poland
This paper discusses research about objective methods, which use psychoacoustic knowledge to estimate the quality of audio signals. The software written especially for this research is presented. This program allows for implementation of the different published methods for evaluation of the quality of perceptually coded audio signals. Protocols such as PAQM, PSQM, NMR, PEAQ, and PESQ are ready to use. All of these algorithms are used for simulation of the auditory system. The software is open for addition to the next protocols as the plug-ins. There is a possibility to change and improve earlier published protocols. Suggested changes, which improve results of objective evaluation, are presented. The criterion of optimization is the difference between results of subjective and objective evaluation.