Psychophysical and physiological evidence for fast binaural processing

The mammalian auditory system is the temporally most precise sensory modality: To localize low-frequency sounds in space, the binaural system can resolve time differences between the ears with microsecond precision. In contrast, the binaural system appears sluggish in tracking changing interaural time differences as they arise from a low-frequency sound source moving along the horizontal plane. For a combined psychophysical and electrophysiological approach, we created a binaural stimulus, called "Phasewarp," that can transmit rapid changes in interaural timing. Using this stimulus, the binaural performance in humans is significantly better than reported previously and comparable with the monaural performance revealed with amplitude-modulated stimuli. Parallel, electrophysiological recordings of binaural brainstem neurons in the gerbil show fast temporal processing of monaural and different types of binaural modulations. In a refined electrophysiological approach that was matched to the psychophysics, the seemingly faster binaural processing of the Phasewarp was confirmed. The current data provide both psychophysical and physiological evidence against a general, hard-wired binaural sluggishness and reconcile previous contradictions of electrophysiological and psychophysical estimates of temporal binaural performance

Implementation and Perceptual Evaluation of a Simulation Method for Coupled Rooms in Higher Order Ambisonics

A fast and perceptively plausible method for rendering acoustic scenarios with moving sources and moving listeners is presented. The method is principally suited for application in dynamic and interactive evaluation environments (e.g., for hearing aid development), psycho-physics with adaptively changing the spatial configuration, or simulation and computer games. The simulation distinguishes between the direct sound, sound reflected and diffracted by objects of limited size, diffuse sound surrounding the listener, e.g., diffuse background sounds and diffuse reverberation, and ’radiating holes’ for simulation of coupled adjacent rooms. Instead of providing its own simulation of room reverberation, the proposed simulation method generates appropriate output signals for external room reverberation simulators (e.g., see contribution by Wendt et al.). The output of such room reverberation simulators is then taken either as diffuse surrounding sound if the listener position is within the simulated room, or as input into a ’radiating hole’, if the listener is in an adjacent room. Subjective evaluations are performed by comparing measured and synthesized transitions between coupled rooms.DFG, FOR 1732, Individualisierte Hörakustik: Modelle, Algorithmen und Systeme für die Sicherstellung der akustischen Wahrnehmung für alle in allen Situatione

Perceptual and Room Acoustical Evaluation of a Computational Efficient Binaural Room Impulse Response Simulation Method

A fast and perceptively plausible method for synthesizing binaural room impulse responses (BRIR) is presented. The method is principally suited for application in dynamic and interactive evaluation environments (e. g., for hearing aid development), psychophysics with adaptively changing room reverberation, or simulation and computer games. In order to achieve a low computational cost, the proposed method is based on a hybrid approach. Using the image source model (ISM; Allen and Berkley [J.Acoust. Soc. Am. Vol. 66(4), 1979]), early reflections are computed in a geometrically exact way, taking into account source and listener positions as well as wall absorption and room geometry approximated by a “shoebox”. The ISM is restricted to a low order and the reverberant tail is generated by a feedback delay network (FDN; Jot and Chaigne [Proc. 90th AES Conv., 1991]), which offers the advantages of a low computational complexity on the one hand and an explicit control of the frequency dependent decay characteristics on the other hand. The FDN approach was extended, taking spatial room properties into account such as room dimensions and different absorption characteristics of the walls. Moreover, the listener orientation and position in the room is considered to achieve a realistic spatial reverberant field. Technical and subjective evaluations were performed by comparing measured and synthesized BRIRs for various rooms. Mostly, a high accuracy both for some common room acoustical parameters and subjective sound properties was found. In addition, an analysis will be presented of several methods to include room geometry in the FDN.DFG, FOR 1732, Individualisierte Hörakustik: Modelle, Algorithmen und Systeme für die Sicherstellung der akustischen Wahrnehmung für alle in allen SituationenDFG, EXC 1077/1, Hören für alle: Modelle, Technologien und Lösungsansätze für Diagnostik, Wiederherstellung und Unterstützung des Hören

Evaluation of Virtual Acoustic Environments with Different Acoustic Level of Detail

Virtual acoustic environments enable the creation and simulation of realistic and ecologically valid daily-life situations with applications in hearing research and audiology. Hereby, reverberant indoor environments play an important role. For real-time applications, simplifications in the room acoustics simulation are required, however, it remains unclear what acoustic level of detail (ALOD) is necessary to capture all perceptually relevant effects. This study investigates the effect of varying ALOD in the simulation of three different real environments, a living room with a coupled kitchen, a pub, and an underground station. ALOD was varied by generating different numbers of image sources for early reflections, or by excluding geometrical room details specific for each environment. The simulations were perceptually evaluated using headphones in comparison to binaural room impulse responses measured with a dummy head in the corresponding real environments. The study assessed the perceived overall difference for a pink pulse, and a speech token. Furthermore, plausibility and externalization were evaluated. The results show that a strong reduction in ALOD is possible while obtaining similar plausibility and externalization as with dummy head recordings. The number and accuracy of early reflections appear less relevant, provided diffuse late reverberation is appropriately accounted for.Comment: This work has been submitted to the I3DA 2023 International Conference on Immersive and 3D Audio for possible publicatio

On the relevance of acoustic measurements for creating realistic virtual acoustic environments

Geometrical approaches for room acoustics simulation have the advantage of requiring limited computational resources while still achieving a high perceptual plausibility. A common approach is using the image source model for direct and early reflections in connection with further simplified models such as a feedback delay network for the diffuse reverberant tail. When recreating real spaces as virtual acoustic environments using room acoustics simulation, the perceptual relevance of individual parameters in the simulation is unclear. Here we investigate the importance of underlying acoustical measurements and technical evaluation methods to obtain high-quality room acoustics simulations in agreement with dummy-head recordings of a real space. We focus on the role of source directivity. The effect of including measured, modelled, and omnidirectional source directivity in room acoustics simulations was assessed in comparison to the measured reference. Technical evaluation strategies to verify and improve the accuracy of various elements in the simulation processing chain from source, the room properties, to the receiver are presented. Perceptual results from an ABX listening experiment with random speech tokens are shown and compared with technical measures for a ranking of simulation approaches.Comment: This work has been submitted to the I3DA 2023 International Conference (IEEE Xplore Digital Library) for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Sensorineural hearing loss enhances auditory sensitivity and temporal integration for amplitude modulation.

Amplitude-modulation detection thresholds (AMDTs) were measured at 40 dB sensation level for listeners with mild-to-moderate sensorineural hearing loss (age: 50-64 yr) for a carrier frequency of 500 Hz and rates of 2 and 20 Hz. The number of modulation cycles, N, varied between two and nine. The data were compared with AMDTs measured for young and older normal-hearing listeners [Wallaert, Moore, and Lorenzi (2016). J. Acoust. Soc. Am. 139, 3088-3096]. As for normal-hearing listeners, AMDTs were lower for the 2-Hz than for the 20-Hz rate, and AMDTs decreased with increasing N. AMDTs were lower for hearing-impaired listeners than for normal-hearing listeners, and the effect of increasing N was greater for hearing-impaired listeners. A computational model based on the modulation-filterbank concept and a template-matching decision strategy was developed to account for the data. The psychophysical and simulation data suggest that the loss of amplitude compression in the impaired cochlea is mainly responsible for the enhanced sensitivity and temporal integration of temporal envelope cues found for hearing-impaired listeners. The data also suggest that, for AM detection, cochlear damage is associated with increased internal noise, but preserved short-term memory and decision mechanisms.N.W. was supported by a grant from Neurelec Oticon Medical. C.L. was supported by two grants from ANR (HEARFIN and HEART projects). S.D.E. was supported by Deutsche Forschungsgemeinschaft (DFG) FOR 1732 (TPE). B.C.J.M. was supported by the EPSRC (UK, grant RG78536). This work was also supported by ANR-11-0001-02 PSL* and ANR-10-LABX-0087. We thank Nihaad Paraouty and two anonymous reviewers for helpful comments and suggestions relating to this study