1:00, AUDIO-P2.1
LOG-MAGNITUDE MODELLING OF AUDITORY TUNING CURVES
L. LIN, E. AMBIKAIRAJAH, W. HOLMES
In this paper, we propose the novel application of a technique for filter design that can accurately fit measured tuning curves for the auditory fibres in the log-magnitude domain. This method provides pole-zero filters with guaranteed stability, and its log-magnitude domain criterion allows tuning curves with very steep slopes to be accurately modelled with an 8th to 10th order pole-zero filter. Thus, this technique can also be used to design a new set of critical band filters with superior frequency domain characteristics compared with the well-known gammatone filter bank. The filter bank designed using this technique has applications in auditory-based speech and audio analysis.

1:00, AUDIO-P2.2
A STUDY ON PERCEPTUAL DISTANCE MEASURE FOR PHASE SPECTRUM OF STIMULI
H. BANNO, K. TAKEDA, F. ITAKURA
This paper describes a perceptual distance measure for phase spectrum based on results from a subjective experiment using stimuli. The stimuli have flat amplitude spectrum and, in a particular frequency band, have a certain group delay value. The experiment was performed using stimuli with different group delay peak values where the group delay center frequencies are fixed, and their associated group delay bandwidths are also fixed. It was found that when the peak values of stimuli are between -1ms and 2ms, they are perceived to be zero phase regardless of their center frequencies and bandwidths. Moreover, when the peak values are less than -8ms or more than 10ms and the bandwidths are less than 1ERB, each of the stimuli are perceived to be similar. Based on these perceptual similarity results, we introduce an ellipsoidal function to estimate the similarity scores with a simple equation. It is found that the estimated similarity scores well approximate the subjective similarity scores.

1:00, AUDIO-P2.3
A MEMORY REDUCTION SCHEME FOR MULTI-CHANNEL ECHO CANCELLER IMPLEMENTATION
C. CHOO, H. ELABD
One of the critical resources of the multi-channel echo canceller is the memory that stores many channels of both tapped delay lines of voice data and filter tap coefficients. In this paper, a simple variable-length/run-length coding scheme for reducing the coefficient memory for multi-channel echo cancellers is proposed. We also describe the corresponding memory system architecture. Simulations based on a bit-accurate Matlab model show that the proposed scheme is effective.

1:00, AUDIO-P2.4
A THEORETICAL STUDY OF INFORMATION TRANSMISSION IN THE AUDITORY SYSTEM USING SIGNAL DETECTION THEORY: FREQUENCY DISCRIMINATION BY NORMAL AND IMPAIRED SYSTEMS
L. HUETTEL, L. COLLINS
In this paper, we have investigated the differences between normal and impaired auditory processing for a frequency discrimination task by analyzing the responses of a computational auditory model using signal detection theory. Two detectors, one using all of the information in the signal, the other using only the number of neural responses, were implemented. An evaluation of the performance differences between the two theoretical detectors and experimental data may provide insight into quantifying the type of information present in the auditory system as well as whether the human auditory system uses this information efficiently. Results support previous hypotheses that, for low- and mid-range frequencies, the auditory system is able to use temporal information to perform frequency discrimination [8]. The results also suggest that some temporal information is represented in the neural spike train, even at high frequencies. However, the ability of the auditory system to use this information deteriorates at higher frequencies.

1:00, AUDIO-P2.5
ACTIVE SPEECH SOURCE LOCALIZATION BY A DUAL COARSE-TO-FINE SEARCH
R. DURAISWAMI, D. ZOTKIN, L. DAVIS
Accurate and fast localization of multiple speech sound sources is a significant problem in videoconferencing systems. Based on the observation that the wavelengths of the sound from a speech source are comparable to the dimensions of the space being searched, and that the source is broadband, we develop an efficient search strategy that finds the source(s) in a given space. The search is made efficient by using coarse-to-fine strategies in both space and frequency. The algorithm is shown to be robust compared to typical TDOA-based estimators and fast enough for real-time implementation. Its performance can further be improved by using constraints from computer vision.

1:00, AUDIO-P2.6
BARK SCALE EQUALIZER DESIGN USING WARPED FILTER
W. PENG, W. SER, M. ZHANG
Bark scale (also called critical band rate in literature) has attracted increasing attention among audio engineers as a good measurement of the frequency resolving ability of human auditory system. In this paper, warped filter technique is applied in bark scale to construct an equalizer for loudspeaker system. The resulted equalizer displays overall better equalization effect in bark scale in the conducted simulation.

1:00, AUDIO-P2.7
MODELING AND EQUALIZATION OF AUDIO SYSTEMS USING KAUTZ FILTERS
T. PAATERO, M. KARJALAINEN, A. HÄRMÄ
Frequency warping using allpass structures or Laguerre filters has found increasingly applications in audio signal processing due to good match with the auditory frequency resolution. Kautz filters are an extension where the frequency warping and related resolution can have more freedom. In this paper we discuss the properties of Kautz filters and how they meet typical requirements found in modeling and equalization of audio systems. Case studies include transfer function modeling of the guitar body and loudspeaker response equalization. MATLAB scripts and demos related to Kautz filter design can be found at http://www.acoustics.hut.fi/software/kautz.

1:00, AUDIO-P2.8
ACOUSTIC EMISSION CLASSIFICATION USING SIGNAL SUBSPACE PROJECTIONS
V. EMAMIAN, M. KAVEH, A. TEWFIK, Z. SHI
In using acoustic emissions (AE) for mechanical diagnostics, one major problem is the differentiation of events due to crack growth in a component from noise of various origins. This work presents two algorithms for automatic clustering and separation of AE events based on multiple features extracted from experimental data. The first algorithm consists of two steps. In the first step, the noise is separated from the events of interest and subsequently removed using a combination of covariance analysis, principal component analysis (PCA), and differential time delay estimates. The second step processes the remaining data using a self-organizing map (SOM), which outputs the noise and AE signals into separate neurons. The algorithm is verified with two sets of data, and a correct classification ratio of over 95% is achieved. The second algorithm characterizes the AE signal subspace based on the principal eigenvectors of the covariance matrix of an ensemble of the AE signals. The latter algorithm has a correct classification ratio over 90%.

1:00, AUDIO-P2.9
EIGENMODE ANALYSIS AND DEGREE OF FREEDOM IN CHAOTIC SEMI-STADIUM SOUND FIELDS
Y. FUJISAKA, Y. TAKAHASHI, M. TOHYAMA
This paper describes eigenfrequency spacing statistics including modal patterns and degrees of freedom in semi-stadium type 2-D field. The authors numerically investigated the sound fields surrounded by 2-D semi-stadium type of boundaries as examples of boundaries where chaotic properties are hidden. One limit of the semi-stadium boundaries is a rectangular which gives a regular field, while another limit is a stadium boundary where the chaotic property emerges. The numerical results show that eigenfrequency spacing in all the cases can be expressed as a family of Gamma distributions extended to a non-integer degree of freedom. This fractal degree of freedom might be interpreted as the degree of freedom of the sound field. For the regular limit case, that is, a rectangular case, the distribution is the exponential distribution with the freedom of unity, while in the chaotic case, that is, the stadium case, it is the Wigner distribution with a degree of freedom of two. Moreover, modal patterns clearly show breaks of the regular pattern of nodal lines seen in a rectangular case as the boundary is deformed from the rectangular to the stadium condition.