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The Better hEAring Rehabilitation (BEAR) project aims to provide a new clinical profiling tool—a test battery—for hearing loss characterization. Although the loss of sensitivity can be efficiently measured using pure-tone audiometry, the assessment of supra-threshold hearing deficits remains a challenge. In contrast to the classical “attenuation-distortion” model, the proposed BEAR approach is based on the hypothesis that the hearing abilities of a given listener can be characterized along two dimensions, reflecting independent types of perceptual deficits (distortions). A data-driven approach provided evidence for the existence of different auditory profiles with different degrees of distortions. Ten tests were included in a test battery, based on their clinical feasibility, time efficiency, and related evidence from the literature. The tests were divided into six categories: audibility, speech perception, binaural processing abilities, loudness perception, spectro-temporal modulation sensitivity, and spectro-temporal resolution. Seventy-five listeners with symmetric, mild-to-severe sensorineural hearing loss were selected from a clinical population. The analysis of the results showed interrelations among outcomes related to high-frequency processing and outcome measures related to low-frequency processing abilities. The results showed the ability of the tests to reveal differences among individuals and their potential use in clinical settings.

An aided sound-field auditory steady state response (ASSR) has the potential to be used to verify the quality of fit of hearing aids on infants. Each aided ear should ideally be tested independently, but it is suspected that binaural testing may be used by clinics to reduce test time. This study simulates ‘clinically conceivable’ dichotic ASSR sound-field conditions to examine the risk of making false judgements due to unchecked binaural effects. Unaided ASSRs were recorded with a clinical two channel EEG system for 15 normally hearing subjects using a three-band CE-ChirpTM stimulus. It was found that the noise corrected power of a response harmonic can be reduced by up to 10 dB by introducing large ITDs equal to half the time period of the stimulus envelope. This could lead to concluding that a hearing aid fitting is poor, even though the fitting would have passed separate monaural ASSR tests (false referral). No effect was detected for simulated lateralisations of the stimulus, which is beneficial for a proposed aided ASSR approach. Full-scalp ASSR recordings show distinct SNR reductions and topographical changes in response to the large ITDs, and demonstrate the vulnerability of ASSR to montage and inter-subject variation. Findings suggest that multi-harmonic detectors could make binaural measurements robust to artificial reductions of response harmonics cause by large ITDs.

INTRODUCTION: One of the most common childhood ear pathologies is otitis media with effusion. The immediate impacts of otitis media are well known, and include fluctuating conductive hearing loss and impaired speech intelligibility. A more subtle influence, present years after the otitis media clears, includes disruptions to binaural cue processing, specifically, the cues that arise when there are differences in the signal arriving at each ear. It is the processing of these difference cues that allows a listener to follow speech in noisy environments and, if compromised in school-age children, may have negative ramifications on classroom listening and academic performance. There is a recognised link between otitis media in early childhood and impaired processing of binaural cues in subsequent years (i.e. longer-term). However, the mechanisms influencing this reported association are yet to be fully explored. OBJECTIVES: This thesis examined the implications of early conductive hearing loss (associated with otitis media) on longer-term binaural processing, at a behaviourally measurable level, and at the level of an auditory evoked potential. DESIGN: Binaural listening ability was determined using standard clinical assessment measures in school-age children with clinical histories documenting hearing and middle-ear status throughout early childhood. Additionally, an evoked potential measure was used as an objective measure of binaural processing ability, with comparisons made between the electrophysiological measure and a behavioural correlate pre- and post-auditory training. RESULTS: The two most important contributions made by this doctoral project were 1) the established relationship between an otitis media related conductive hearing loss history in the first four years of life and reduced spatial processing ability at school-age, and 2) the findings that suggest spatial processing is not completely dependent upon the activity at the subcortical centres. IMPLICATIO

Binaural hearing studies show that the auditory system uses the phase-difference information in the auditory stimuli for localization of a sound source. Motivated by this finding, we present a method for demodulation of amplitude-modulated-frequency-modulated (AM-FM) signals using a signal and its arbitrary phase-shifted version. The demodulation is achieved using two allpass filters, whose impulse responses are related through the fractional Hilbert transform (FrHT). The allpass filters are obtained by cosine-modulation of a zero-phase flat-top prototype halfband lowpass filter. The outputs of the filters are combined to construct an analytic signal (AS) from which the AM and FM are estimated. We show that, under certain assumptions on the signal and the filter structures, the AM and FM can be obtained exactly. The AM-FM calculations are based on the quasi-eigenfunction approximation. We then extend the concept to the demodulation of multicomponent signals using uniform and non-uniform cosine-modulated filterbank (FB) structures consisting of flat bandpass filters, including the uniform cosine-modulated, equivalent rectangular bandwidth (ERB), and constant-Q filterbanks. We validate the theoretical calculations by considering application on synthesized AM-FM signals and compare the performance in presence of noise with three other multiband demodulation techniques, namely, the Teager-energy-based approach, the Gabor's AS approach, and the linear transduction filter approach. We also show demodulation results for real signals., QC 20140701

In this paper we present a new approach for estimating the number of active speech sources in the presence of interfering noise sources and reverberation. First, a binaural front-end is used to detect the spatial positions of all active sound sources, resulting in a binary mask for each candidate position. Then, each candidate position is characterized by a set of features. In addition to exploiting the overall spectral shape, a new set of mask-based features is proposed which aims at characterizing the pattern of the estimated binary mask. The decision stage for detecting a speech source is based on a support vector machine (SVM) classifier. A systematic analysis shows that the proposed algorithm is able to blindly determine the number and the corresponding spatial positions of speech sources in multisource scenarios and generalizes well to unknown acoustic conditions

The ability of eight normal-hearing listeners and fourteen listeners with sensorineural hearing loss to detect and identify pitch contours was measured for binaural-pitch stimuli and salience-matched monaurally detectable pitches. In an effort to determine whether impaired binaural pitch perception was linked to a specific deficit, the auditory profiles of the individual listeners were characterized using measures of loudness perception, cognitive ability, binaural processing, temporal fine structure processing, and frequency selectivity, in addition to common audiometric measures. Two of the listeners were found not to perceive binaural pitch at all, despite a clear detection of monaural pitch. While both binaural and monaural pitches were detectable by all other listeners, identification scores were significantly lower for binaural than for monaural pitch. A total absence of binaural pitch sensation coexisted with a loss of a binaural signal-detection advantage in noise, without implying reduced cognitive function. Auditory filter bandwidths did not correlate with the difference in pitch identification scores between binaural and monaural pitches. However, subjects with impaired binaural pitch perception showed deficits in temporal fine structure processing. Whether the observed deficits stemmed from peripheral or central mechanisms could not be resolved here, but the present findings may be useful for hearing loss characterization. (C) 2012 Acoustical Society of America. [http://dx.doi.org/10.1121/1.3689554]

In this paper we present a new approach for estimating the number of active speech sources in the presence of interfering noise sources and reverberation. First, a binaural front-end is used to detect the spatial positions of all active sound sources, resulting in a binary mask for each candidate position. Then, each candidate position is characterized by a set of features. In addition to exploiting the overall spectral shape, a new set of mask-based features is proposed which aims at characterizing the pattern of the estimated binary mask. The decision stage for detecting a speech source is based on a support vector machine (SVM) classifier. A systematic analysis shows that the proposed algorithm is able to blindly determine the number and the corresponding spatial positions of speech sources in multisource scenarios and generalizes well to unknown acoustic conditions

In this paper we present a new approach for estimating the number of active speech sources in the presence of interfering noise sources and reverberation. First, a binaural front-end is used to detect the spatial positions of all active sound sources, resulting in a binary mask for each candidate position. Then, each candidate position is characterized by a set of features. In addition to exploiting the overall spectral shape, a new set of mask-based features is proposed which aims at characterizing the pattern of the estimated binary mask. The decision stage for detecting a speech source is based on a support vector machine (SVM) classifier. A systematic analysis shows that the proposed algorithm is able to blindly determine the number and the corresponding spatial positions of speech sources in multisource scenarios and generalizes well to unknown acoustic conditions

This dissertation investigates aspects of auditory scene analysis such as the detection of a new object in the environment. Specifically I try to learn about these processes by studying the temporal dynamics of magnetic signals recorded from outside the scalp of human listeners, and comparing these dynamics with psychophysical measures. In total nine behavioral and Magneto-encephalography (MEG) brain-imaging experiments are reported. These studies relate to the extraction of tonal targets from background noise and the detection of change within ongoing sounds. The MEG deflections we observe between 50-200 ms post transition reflect the first stages of perceptual organization. I interpret the temporal dynamics of these responses in terms of activation of cortical systems that participate in the detection of acoustic events and the discrimination of targets from backgrounds. The data shed light on the statistical heuristics with which our brains sample, represent, and detect changes in the world, including changes that are not the immediate focus of attention. In particular, the asymmetry of responses to transitions between 'order' and 'disorder' within a stimulus can be interpreted in terms of different requirements for temporal integration. The similarity of these transition-responses with commonly observed onset M50 and M100 auditory-evoked fields allows us to suggest a hypothesis as to their underlying functional significance, which so far has remained unclear. The comparison of MEG and psychophysics demonstrates a striking dissociation between higher level mechanisms related to conscious detection and the lower-level, pre-attentive cortical mechanisms that sub-serve the early organization of auditory information. The implications of these data for the processes that underlie the creation of perceptual representations are discussed. A comparison of the behavior of normal and dyslexic subjects in a tone-in-noise detection task revealed a general difficulty in extra

Phase I has resulted in advances in computational methods, assessments of current strengths and weakness, and assessments of the range of potential applications and their performance requirements. The progress and results from Phase I show that the technology is very promising. However, it has also become clear that the problem is quite challenging, and significant technical weaknesses remain. Phase II would aim to overcome the most significant weaknesses preventing practical levels of performance. These are considered to be: inadequate performance on unvoiced speech materials, weak processing algorithms that mandate large amounts of computation and impose latencies that are too long for near-real-time applications.

Physical and behavioral methods were employed to determine the characteristics of a binaural microphone array and its ability to support the localization of sources of sound. The gain pattern and output delay of the array were made and compared to those of an acoustic mannequin. Three behavioral methods of assessing the adequacy of binaural information provided by the array were employed. These include (a) measuring the minimum audible angle, (b) defining the limit of image lateralization, and (c) determining the accuracy with which listeners could point the array at an acoustic source. Insights about transformations produced by the array were provided by a modeling effort. The data indicate that the present design would provide reliable information when it is used as a dynamic pointing device.

The objective of this report is to better understand the role of binaural processing in complex multi-sound source acoustic environments. Dr Grange worked on the topic of binaural pitch, sometimes called Huggins pitch.

Our research concerned the manners by which the monaural and binaural auditory systems tial progress was made consistent with the objectives process information in complex sounds. SubStan outlined in the original proposal in three areas: (1) New electronic equipment, including a NeXT computer was purchased, installed and interfaced with the existing laboratory. Software was developed for generating the necessary complex digital stimuli and for running behavioral experiments utilizing those stimuli. (2) Monaural experiments showed that the CMR is not obtained successively and is reduced or non-existent when the flanking bands are pulsed rather than presented continuously. Binaural investigations revealed that the detectability of a tonal target in a masking level difference paradigm could be degraded by the presence of a spectrally remote interfering tone. (3) In collaboration with Dr. Richard Stem, theoretical efforts included the explication and evaluation of a weighted-image model of binaural hearing, attempts to extend the Stern-Colbum position-variable model to account for many crucial lateralization and localization data gathered over the past 50 years and the continuation of efforts to incorporate into a general model notions that lateralization and localization of spectrally-rich stimuli depends upon the patterns of neural activity within a plane defined by frequency and interaural delay.

Sounds produced by acoustic sources are localized and detected on the basis of differences in the time of arrival between the two ears and differences in the levels at the two ears. Most real world sounds are spectrally complex, consisting of energy distributed across many frequencies. In general, the auditory system must make judgments regarding the location of acoustic sources on the basis of these interaural differences, even though their distribution across frequency may be quite complex. This proposal has sought to understand the processes by which the binaural auditory system combines interaural information across the spectrum. The auditory system is spectrally synthetic, averaging information across the frequency domain, when the signal consists of relatively few components. Under these circumstances, the system behaves as though all components arise from the same spatial location.