We will have a special HRC seminar next Wednesday, July 8, 2009.
On July 8 at 10:30 am, Prof. Jonas Braasch from RPI will talk about
some of his work on a new model of the precedence effect based on
autocorrelation. The talk will be in room 203 of 44 Cummington Street.
Refreshment will be provided.

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Wednesday, July 8, 2009
10:30 AM -- noon
Room 203, 44 Cummington St.

Prof. Jonas Braasch
Head of Communication Acoustics and Aural Architecture Research Lab
School of Architecture, Rensselaer Polytechnic Institute (RPI)

Title: Investigating the precedence effect for non-impulsive sounds:
Psychoacoustic evidence and simulation

Abstract:
The human ability to localize a direct sound source in the presence of
reflected sounds is well known as localization dominance due to the
precedence effect, formerly also called "the law of the first
wavefront." This presentation focuses on human ability to localize
non-impulsive sounds in presence of a single reflection. During the
experiments, which will be reported here, the bandwidth and
characteristics of the stimuli (noise vs. harmonic complexes) were
varied. The second part of the talk will be dedicated to the
simulation of these experiments using a newly designed binaural model.
In this model, an auto-correlation algorithm determines the delay
between lead and lag and their amplitude ratio for both channels. An
inverse filter is then used to eliminate the lag signal, before it is
localized with a standard localization algorithm. Interestingly, the
filter contains both inhibitory and excitatory elements, and the
filter’s impulse response looks somewhat similar to the response of a
chopper cell. The algorithm operates robustly on top of a model of the
auditory periphery (gammatone filterbank, halfwave rectification). Due
to its linear nature, the model performs better if the full waveform
is reconstructed by subtracting a delayed version of the
halfwave-rectified signal, with a delay time that corresponds to half
the period of each frequency band’s center frequency. The model is
able to simulate a number of experiments with ongoing stimuli, and
performs robustly with onset-truncated and interaural-level-difference
based stimuli that were previously investigated psychoacoustically by
Dizon and Colburn. The model can also be used to demonstrate the Haas
Effect.

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