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Bertrand Delgutte - One of the best experts on this subject based on the ideXlab platform.

  • neural itd coding with bilateral cochlear implants effect of binaurally coherent jitter
    Journal of Neurophysiology, 2012
    Co-Authors: Kenneth E Hancock, Bertrand Delgutte, Yoojin Chung
    Abstract:

    Poor sensitivity to the Interaural Time Difference (ITD) constrains the ability of human bilateral cochlear implant users to listen in everyday noisy acoustic environments. ITD sensitivity to perio...

  • a physiologically based model of Interaural Time Difference discrimination
    The Journal of Neuroscience, 2004
    Co-Authors: Kenneth E Hancock, Bertrand Delgutte
    Abstract:

    Interaural Time Difference (ITD) is a cue to the location of sounds containing low frequencies and is represented in the inferior colliculus (IC) by cells that respond maximally at a particular best delay (BD). Previous studies have demonstrated that single ITD-sensitive cells contain sufficient information in their discharge patterns to account for ITD acuity on the midline (ITD = 0). If ITD discrimination were based on the activity of the most sensitive cell available ("lower envelope hypothesis"), then ITD acuity should be relatively constant as a function of ITD. In response to broadband noise, however, the ITD acuity of human listeners degrades as ITD increases. To account for these results, we hypothesize that pooling of information across neurons is an essential component of ITD discrimination. This report describes a neural pooling model of ITD discrimination based on the response properties of ITD-sensitive cells in the IC of anesthetized cats. Rate versus ITD curves were fit with a cross-correlation model of ITD sensitivity, and the parameters were used to constrain a population model of ITD discrimination. The model accurately predicts ITD acuity as a function of ITD for broadband noise stimuli when responses are pooled across best frequency (BF). Furthermore, ITD tuning based solely on a system of internal delays is not sufficient to predict ITD acuity in response to 500 Hz tones, suggesting that acuity is likely refined by additional mechanisms. The physiological data confirms evidence from the guinea pig that BD varies systematically with BF, generalizing the observation across species.

Jan Wouters - One of the best experts on this subject based on the ideXlab platform.

  • theoretical analysis of binaural multimicrophone noise reduction techniques
    IEEE Transactions on Audio Speech and Language Processing, 2010
    Co-Authors: Bram Cornelis, Simon Doclo, Marc Moonen, T Van Dan Bogaert, Jan Wouters
    Abstract:

    Binaural hearing aids use microphone signals from both left and right hearing aid to generate an output signal for each ear. The microphone signals can be processed by a procedure based on speech distortion weighted multichannel Wiener filtering (SDW-MWF) to achieve significant noise reduction in a speech + noise scenario. In binaural procedures, it is also desirable to preserve binaural cues, in particular the Interaural Time Difference (ITD) and Interaural level Difference (ILD), which are used to localize sounds. It has been shown in previous work that the binaural SDW-MWF procedure only preserves these binaural cues for the desired speech source, but distorts the noise binaural cues. Two extensions of the binaural SDW-MWF have therefore been proposed to improve the binaural cue preservation, namely the MWF with partial noise estimation (MWF-eta) and MWF with Interaural transfer function extension (MWF-ITF). In this paper, the binaural cue preservation of these extensions is analyzed theoretically and tested based on objective performance measures. Both extensions are able to preserve binaural cues for the speech and noise sources, while still achieving significant noise reduction performance.

  • binaural multi channel wiener filtering for hearing aids preserving Interaural Time and level Differences
    International Conference on Acoustics Speech and Signal Processing, 2006
    Co-Authors: Thomas Klasen, Simon Doclo, Marc Moonen, T Van Den Bogaert, Jan Wouters
    Abstract:

    This paper presents an extension of the binaural multi-channel Wiener filtering algorithm discussed in T.J. Klasen et al. (2005). The goal of this paper is to preserve both the Interaural Time Difference (ITD) and Interaural level Difference (ILD) of the speech and noise components. This is done by extending the cost function to incorporate terms for the Interaural transfer functions (ITF) of the speech and noise components. Using weights, the emphasis on the preservation of the ITFs can be controlled in addition to the emphasis on noise reduction. Adapting these parameters allows one to preserve the ITFs of the speech and noise component, and therefore ITD and ILD cues, while enhancing the signal-to-noise ratio

  • extension of the multi channel wiener filter with itd cues for noise reduction in binaural hearing aids
    Workshop on Applications of Signal Processing to Audio and Acoustics, 2005
    Co-Authors: Simon Doclo, Jan Wouters, Rong Dong, Thomas Klasen, S Haykin, Marc Moonen
    Abstract:

    This paper presents a novel extension of the multi-channel Wiener filter (MWF) for noise reduction in binaural hearing aids, taking into account binaural localisation cues. By adding a term related to the Interaural Time Difference (ITD) cue of the noise component to the cost function of the MWF, both the ITD cues of the speech and the noise component can be preserved, in addition to significantly improving the signal-to-noise ratio of the microphone signals

Francart Tom - One of the best experts on this subject based on the ideXlab platform.

  • A framework for computational modelling of Interaural Time Difference discrimination of normal and hearing-impaired listeners
    'Acoustical Society of America (ASA)', 2018
    Co-Authors: Moncada-torres Arturo, Epp Bastian, Prokopiou Andreas, Wouters Jan, Yoshi, Suyash N, Francart Tom
    Abstract:

    Different computational models have been developed to study the Interaural Time Difference (ITD) perception. However, only few have used a physiologically inspired architecture to study ITD discrimination. Furthermore, they do not include aspects of hearing impairment. In this work, a framework was developed to predict ITD thresholds in listeners with normal and impaired hearing. It combines the physiologically inspired model of the auditory periphery proposed by Zilany, Bruce, Nelson, and Carney [(2009). J. Acoust. Soc. Am. 126(5), 2390–2412] as a front end with a coincidence detection stage and a neurometric decision device as a back end. It was validated by comparing its predictions against behavioral data for narrowband stimuli from literature. The framework is able to model ITD discrimination of normal-hearing and hearing-impaired listeners at a group level. Additionally, it was used to explore the effect of different proportions of outer- and inner-hair cell impairment on ITD discrimination.status: Published onlin

  • Interaural Time Difference Perception with a Cochlear Implant and a Normal Ear
    'Springer Science and Business Media LLC', 2018
    Co-Authors: Francart Tom, Wiebe Konstantin, Wesarg Thomas
    Abstract:

    Currently there is a growing population of cochlear-implant (CI) users with (near) normal hearing in the non-implanted ear. This configuration is often called SSD (single-sided deafness) CI. The goal of the CI is often to improve spatial perception, so the question raises to what extent SSD CI listeners are sensitive to Interaural Time Differences (ITDs). In a controlled lab setup, sensitivity to ITDs was investigated in 11 SSD CI listeners. The stimuli were 100-pps pulse trains on the CI side and band-limited click trains on the acoustic side. After determining level balance and the delay needed to achieve synchronous stimulation of the two ears, the just noticeable Difference in ITD was measured using an adaptive procedure. Seven out of 11 listeners were sensitive to ITDs, with a median just noticeable Difference of 438 μs. Out of the four listeners who were not sensitive to ITD, one listener reported binaural fusion, and three listeners reported no binaural fusion. To enable ITD sensitivity, a frequency-dependent delay of the electrical stimulus was required to synchronize the electric and acoustic signals at the level of the auditory nerve. Using subjective fusion measures and refined by ITD sensitivity, it was possible to match a CI electrode to an acoustic frequency range. This shows the feasibility of these measures for the allocation of acoustic frequency ranges to electrodes when fitting a CI to a subject with (near) normal hearing in the contralateral ear.status: publishe

  • Functional modelling of Interaural Time Difference discrimination in acoustical and electrical hearing
    'IOP Publishing', 2017
    Co-Authors: Prokopiou Andreas, Moncada-torres Arturo, Wouters Jan, Francart Tom
    Abstract:

    OBJECTIVE: Interaural Time Differences (ITDs) are important for sound source localisation. We present a model to predict the just noticeable Differences (JNDs) in ITD discrimination for normal hearing and electric stimulation through a cochlear implant. APPROACH: We combined periphery models of acoustic and electric stimulation with a novel JND in the ITD estimation stage, which consists of a shuffled cross correlogram and a binary classifier characterisation method. Furthermore, an evaluation framework is presented based on a large behavioural dataset. MAIN RESULTS: The model correctly predicts behavioural observations for unmodulated stimuli (such as pure tones and electric pulse trains) and modulated stimuli for modulation frequencies below 30 Hz. For higher modulation frequencies, the model predicts the observed behavioural trends, but tends to estimate higher ITD sensitivity. SIGNIFICANCE: The presented model can be used to investigate the implications of modifying the stimulus waveform on ITD sensitivity, and as such be applied in investigating sound encoding strategies.journal_title: Journal of Neural Engineering article_type: paper article_title: Functional modelling of Interaural Time Difference discrimination in acoustical and electrical hearing copyright_information: © 2017 IOP Publishing Ltd date_received: 2016-09-20 date_accepted: 2017-05-02 date_epub: 2017-06-13status: publishe

  • Model-based Analysis of Interaural Time Difference Perception in Normal & Hearing Impaired Listeners
    2016
    Co-Authors: Moncada-torres Arturo, Joshi, Suyash N, Epp Bastian, Francart Tom
    Abstract:

    Interaural Time Differences (ITDs) are a fundamental cue for sound localization. Sensorineural hearing impaired (HI) listeners frequently have worsened localization and lateralization performance compared to normal hearing (NH) listeners, also reflected in deficient detection and discrimination of ITDs. It has been suggested that ITDs are processed by specialized cells that receive input from the auditory nerve (AN) from both ears and function as coincidence detectors. In this work, we developed a physiologically motivated model framework to evaluate temporal coding of ITDs at the periphery level of NH and HI listeners. AN responses to acoustic stimuli from both ears (in the form of spikes) with introduced ITDs (including a reference condition with ITD = 0 μs) were simulated using the phenomenological model proposed by Zilany et al. (2009). Next, we utilized shuffled cross-correlograms (SCCs, Joris, et al., 2006) to quantify the encoded ITD across the AN of both channels. Assuming that the auditory system favors the perception of smaller ITDs, we corrected the SCC curves using the weighting function proposed by Shackleton et al. (1992). Then, we predicted the imposed ITD by choosing the global maximum. As a decision variable, the distributions of the predicted reference and imposed ITDs were processed to obtain a receiver operating characteristic (ROC) in a 2 alternative force choice (AFC) procedure. This allowed us to compute the ITD just noticeable Difference (JND) as the 75 % point of the psychometric curve. Finally, we evaluated the model by comparing the simulated ITD JNDs against literature behavioural data using bandpass noise with a center frequency and a bandwidth of 500 and 100 Hz, respectively. For the HI case, we used the same framework, but modified the AN model to account for different degrees of inner/outer haircell (IHC/OHC) impairment based on audiogram information. The proposed framework successfully predicted bandpass noise ITD JNDs of NH listeners. In the case of HI listeners, the model was able to account for trends in the data, although the high variability of participants' performance make the comparison to data difficult. These results provide the basis for a model-based quantification of ITD coding in NH and HI listeners at the periphery level. Future work will be focused in using the current approach to predict ITD discrimination performance in listeners with acoustic and electric hearing to optimize the representation of spatial information in hearing devices signal processing.status: publishe

  • Optimizing Binaural Cue Perception with Combined Cochlear Implant and Acoustic Stimulation
    Association for Research in Otolaryngology, 2015
    Co-Authors: Francart Tom, Lenssen Anneke, Spirrov Dimitar, Wouters Jan
    Abstract:

    Currently, bimodal listeners are normally fitted with a standard cochlear implant (CI) sound processor and hearing aid. This configuration has been shown to be advantageous compared to only the CI. We recently found that bimodal listeners with sufficient residual hearing can be sensitive to binaural cues: Interaural level Differences and Interaural Time Differences in the envelope and transients of the signal. However, with current clinical devices bimodal listeners do not appear to make advantage of binaural cues, due to poor cue transmission by the devices. We have developed two sound processing strategies to improve this: SCORE bimodal and MEnS. The SCORE bimodal strategy aims to equalise loudness growth for both modalities using real-Time application of models of loudness perception for acoustic and electric stimulation. As SCORE was found to improve loudness perception and not to interfere with speech perception and, it seems beneficial to implement it in clinical devices. The MEnS strategy introduces temporal modulations on all stimulated electrodes, synchronously with modulations present in the acoustic signal, based on measurement of the peaks occurring at the rate of the fundamental frequency in voiced phonemes. Compared to the ACE strategy, Interaural Time Difference detection and Interaural-Time-Difference based lateralisation was significantly improved with just noticeable Differences with MEnS well within the physically relevant range. The application of these two strategies could lead to improved sound source localisation and binaural unmasking with bimodal stimulation.status: publishe

Benedikt Grothe - One of the best experts on this subject based on the ideXlab platform.

  • adjustment of Interaural Time Difference analysis to sound level
    2010
    Co-Authors: Ida Siveke, Benedikt Grothe, Christian Leibold, Katharina Kaiser, Lutz Wiegrebe
    Abstract:

    To localize low-frequency sound sources in azimuth, the binaural system compares the timing of sound waves at the two ears with microsecond precision. A similarly high precision is also seen in the binaural processing of the envelopes of high-frequency complex sounds. Both for low- and high-frequency sounds, Interaural Time Difference (ITD) acuity is to a large extent independent of sound level. The mechanisms underlying this level-invariant extraction of ITDs by the binaural system are, however, only poorly understood. We use high-frequency pip trains with asymmetric and dichotic pip envelopes in a combined psychophysical, electrophysiological, and modeling approach. Although the dichotic envelopes cannot be physically matched in terms of ITD, the match produced perceptually by humans is very reliable, and it depends systematically on the overall sound level. These data are reflected in neural responses from the gerbil lateral superior olive and lateral lemniscus. The results are predicted in an existing temporal-integration model extended with a level-dependent threshold criterion. These data provide a very sensitive quantification of how the peripheral temporal code is conditioned for binaural analysis.

  • Interaural Time Difference processing in the mammalian medial superior olive the role of glycinergic inhibition
    The Journal of Neuroscience, 2008
    Co-Authors: Michael Pecka, Antje Brand, Oliver Behrend, Benedikt Grothe
    Abstract:

    The dominant cue for localization of low-frequency sounds are microsecond Differences in the Time-of-arrival of sounds at the two ears [Interaural Time Difference (ITD)]. In mammals, ITD sensitivity is established in the medial superior olive (MSO) by coincidence detection of excitatory inputs from both ears. Hence the relative delay of the binaural inputs is crucial for adjusting ITD sensitivity in MSO cells. How these delays are constructed is, however, still unknown. Specifically, the question of whether inhibitory inputs are involved in timing the net excitation in MSO cells, and if so how, is controversial. These inhibitory inputs derive from the nuclei of the trapezoid body, which have physiological and structural specializations for high-fidelity temporal transmission, raising the possibility that well Timed inhibition is involved in tuning ITD sensitivity. Here, we present physiological and pharmacological data from in vivo extracellular MSO recordings in anesthetized gerbils. Reversible blockade of synaptic inhibition by iontophoretic application of the glycine antagonist strychnine increased firing rates and significantly shifted ITD sensitivity of MSO neurons. This indicates that glycinergic inhibition plays a major role in tuning the delays of binaural excitation. We also tonically applied glycine, which lowered firing rates but also shifted ITD sensitivity in a way analogous to strychnine. Hence tonic glycine application experimentally decoupled the effect of inhibition from the timing of its inputs. We conclude that, for proper ITD processing, not only is inhibition necessary, but it must also be precisely Timed.

  • precise inhibition is essential for microsecond Interaural Time Difference coding
    Nature, 2002
    Co-Authors: Antje Brand, Oliver Behrend, Torsten Marquardt, David Mcalpine, Benedikt Grothe
    Abstract:

    Microsecond Differences in the arrival Time of a sound at the two ears (Interaural Time Differences, ITDs) are the main cue for localizing low-frequency sounds in space. Traditionally, ITDs are thought to be encoded by an array of coincidence-detector neurons, receiving excitatory inputs from the two ears via axons of variable length ('delay lines'), to create a topographic map of azimuthal auditory space(1,2). Compelling evidence for the existence of such a map in the mammalian ITD detector, the medial superior olive (MSO), however, is lacking. Equally puzzling is the role of a-temporally very precise(3)-glycine-mediated inhibitory input to MSO neurons. Using in vivo recordings from the MSO of the Mongolian gerbil, we found the responses of ITD-sensitive neurons to be inconsistent with the idea of a topographic map of auditory space. Moreover, local application of glycine and its antagonist strychnine by iontophoresis (through glass pipette electrodes, by means of an electric current) revealed that precisely Timed glycine-controlled inhibition is a critical part of the mechanism by which the physiologically relevant range of ITDs is encoded in the MSO. A computer model, simulating the response of a coincidence-detector neuron with bilateral excitatory inputs and a temporally precise contralateral inhibitory input, supports this conclusion.

Simon Doclo - One of the best experts on this subject based on the ideXlab platform.

  • coherence preservation in multi channel wiener filtering based noise reduction for binaural hearing aids
    International Conference on Acoustics Speech and Signal Processing, 2013
    Co-Authors: Daniel Marquardt, Volker Hohmann, Simon Doclo
    Abstract:

    Besides noise reduction an important objective of binaural speech enhancement algorithms is the preservation of the binaural cues, i.e. the Interaural Level Difference and the Interaural Time Difference of all sound sources. Recently, extensions of the binaural Multi-channel Wiener filter (MWF) have been presented, which aim to preserve the binaural cues of the residual noise component. However, since these algorithms aim to preserve the Interaural Transfer Function (ITF), they are well-suited only for directional noise sources but not for, e.g. spatially isotropic noise, which can not be fully described by the ITF. In this paper, we present an extension of the binaural MWF, aiming to preserve the Interaural Coherence of the residual noise component. Experimental results using spatially isotropic noise show that the proposed algorithm yields a good preservation of the Interaural Coherence without significantly degrading the output SNR compared to the binaural MWF and the binaural MWF with ITF preservation.

  • theoretical analysis of binaural multimicrophone noise reduction techniques
    IEEE Transactions on Audio Speech and Language Processing, 2010
    Co-Authors: Bram Cornelis, Simon Doclo, Marc Moonen, T Van Dan Bogaert, Jan Wouters
    Abstract:

    Binaural hearing aids use microphone signals from both left and right hearing aid to generate an output signal for each ear. The microphone signals can be processed by a procedure based on speech distortion weighted multichannel Wiener filtering (SDW-MWF) to achieve significant noise reduction in a speech + noise scenario. In binaural procedures, it is also desirable to preserve binaural cues, in particular the Interaural Time Difference (ITD) and Interaural level Difference (ILD), which are used to localize sounds. It has been shown in previous work that the binaural SDW-MWF procedure only preserves these binaural cues for the desired speech source, but distorts the noise binaural cues. Two extensions of the binaural SDW-MWF have therefore been proposed to improve the binaural cue preservation, namely the MWF with partial noise estimation (MWF-eta) and MWF with Interaural transfer function extension (MWF-ITF). In this paper, the binaural cue preservation of these extensions is analyzed theoretically and tested based on objective performance measures. Both extensions are able to preserve binaural cues for the speech and noise sources, while still achieving significant noise reduction performance.

  • binaural multi channel wiener filtering for hearing aids preserving Interaural Time and level Differences
    International Conference on Acoustics Speech and Signal Processing, 2006
    Co-Authors: Thomas Klasen, Simon Doclo, Marc Moonen, T Van Den Bogaert, Jan Wouters
    Abstract:

    This paper presents an extension of the binaural multi-channel Wiener filtering algorithm discussed in T.J. Klasen et al. (2005). The goal of this paper is to preserve both the Interaural Time Difference (ITD) and Interaural level Difference (ILD) of the speech and noise components. This is done by extending the cost function to incorporate terms for the Interaural transfer functions (ITF) of the speech and noise components. Using weights, the emphasis on the preservation of the ITFs can be controlled in addition to the emphasis on noise reduction. Adapting these parameters allows one to preserve the ITFs of the speech and noise component, and therefore ITD and ILD cues, while enhancing the signal-to-noise ratio

  • extension of the multi channel wiener filter with itd cues for noise reduction in binaural hearing aids
    Workshop on Applications of Signal Processing to Audio and Acoustics, 2005
    Co-Authors: Simon Doclo, Jan Wouters, Rong Dong, Thomas Klasen, S Haykin, Marc Moonen
    Abstract:

    This paper presents a novel extension of the multi-channel Wiener filter (MWF) for noise reduction in binaural hearing aids, taking into account binaural localisation cues. By adding a term related to the Interaural Time Difference (ITD) cue of the noise component to the cost function of the MWF, both the ITD cues of the speech and the noise component can be preserved, in addition to significantly improving the signal-to-noise ratio of the microphone signals