Auditory Scene Analysis

 

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  Loudspeakersetup in an anechoic chamber Copyright: FPA

"I can hardly understand you! It is too loud here" - a typical statement by a person in a busy restaurant, during an event or in many other everyday situations. The required ability here to auditorily differentiate a signal source from various useful and interfering signals has its roots in binaural hearing (hearing with both ears). Basic experimenting regarding binaural hearing has however so far only been carried out in laboratories and with very simple means.

In this research area we examine for example how room acoustics affects auditory attention. With the aid of computer-generated acoustic scenarios we investigate the effect of sound reflections on perception.

Applying hearing tests we explore the processing mechanisms of persons with normal hearing and those with impaired hearing (children, adults, people with age-related hearing loss, people using hearing aids, Cochlea Implants).

Auditory perception of sound reflections and localization of dynamic scenarios

To orientate himself in complex surroundings a human being beside his sense of vision also needs acoustic information. For an acoustic orientation in his surroundings a person uses the early reflections of confining areas (walls, ceilings, floors, large objects) and their relation to the sound source.

Using hearing tests we research the auditory perception of complex acoustic scenarios of test persons with normal hearing, impaired hearing and blind persons. These scenarios can be free field conditions, large rooms or outdoor scenarios (e.g. orientation in the city).

Experiments to test attention in dynamic acoustically complex scenarios

With the aid of Acoustic Virtual Reality and Binaural Technology we focus on researching in virtual acoustic scenarios the effects of individual parameters (room acoustics, sound reflection, etc.), for example on selective auditory attention.

 

Spatial reproduction of virtual acoustic environments

Spherical loudspeaker arrays allow virtual acoustic environments with simulated room acoustics to be reproduced in a plausible or authentic way using various spatial reproduction methods. The loudspeaker array installed in the anechoic chamber of the institute consists of 68 coaxial loudspeakers, sampling a spherical cap with a radius of 1.35 m on an equal-area grid. A network-based audio transmission and low-noise amplifiers enable low reproduction latencies and a high signal-to-noise ratio. Individually designed filters with finite impulse response and 512 taps per channel are used to minimize manufacturing tolerances and equalize the loudspeaker transfer functions. Time delays and corresponding level adjustments further help to minimize radial positioning errors. For sound field synthesis in the center of the array, methods such as vector-based amplitude panning or higher-order Ambisonics are suitable. Using acoustic crosstalk cancellation and a motion tracking system, also binaural signals can be dynamically reproduced over loudspeakers. Therefore, the array represents a flexible tool for acoustic measurements and objective as well as perceptual evaluations.

For further details on implementation and evaluation, please refer to the following publication:

Pausch F, Behler G & Fels J. 2020. SCaLAr – A surrounding spherical cap loudspeaker array for flexible generation and evaluation of virtual acoustic environments. Acta Acust., 4(5):19, 2020