117 research outputs found
The Neurophysiological Bases of Auditory Perception
No full textFrom its inception in 1969, The International Symposium on Hearing has been a forum of excellence for debating the neurophysiological basis of auditory perception, with computational models as tools to test and unify physiological and perceptual theories. Every paper in this symposium includes two of the following: auditory physiology, psychophysics or modeling. The topics range from cochlear physiology to auditory attention and learning. The Neurophysiological Bases of Auditory Perception has a bottom-up structure from ?simpler? physiological to more ?complex? perceptual phenomena and follows the order of presentations at the 2009 meeting. The volume describes state-of-the-art knowledge on the most current topics of auditory science and will act as a valuable resource to stimulate further research
Beyond the Audiogram: Identifying and Modeling Patterns of Hearing Deficits
No full textThe choice of a hearing aid and its tuning parameters should benefit from a more detailed assessment of a patient?s hearing than that occurs at present in clinical practice. The process of fitting and tuning might be facilitated even more if these data were used to generate a computer model of the patient?s hearing. A number of hearing impaired patients have been tested using a range of tests that were devised to be easy to administer under automatic computer control and easy for the, often elderly, listeners to use. The principal finding is that there is an unexpected variation among patients in the patterns of impairment that are revealed by the tests. This is true even when the patients have similar audiograms. The data have been used to develop individual computer models of the patients? hearing which we call ?hearing dummies.? These dummies have been successfully evaluated using the same automated tests that were used to collect the original data. The creation of these dummies raises interesting questions about the basis of different forms of hearing pathology and point to a future where all forms of hearing impairment and their treatment might be diagnosed in terms of the underlying pathology rather than the symptomatology as at present
A frequency-selective feedback model of auditory efferent suppression and its implications for the recognition of speech in noise
No full textThe potential contribution of the peripheral auditory efferent system to our understanding of speech in a background of competing noise was studied using a computer model of the auditory periphery and assessed using an automatic speech recognition system. A previous study had shown that a fixed efferent attenuation applied to all channels of a multi-channel model could improve the recognition of connected digit triplets in noise [G. J. Brown, R. T. Ferry, and R. Meddis, J. Acoust. Soc. Am. 127, 943?954 (2010)]. In the current study an anatomically justified feedback loop was used to automatically regulate separate attenuation values for each auditory channel. This arrangement resulted in a further enhancement of speech recognition over fixed-attenuation conditions. Comparisons between multi-talker babble and pink noise interference conditions suggest that the benefit originates from the model?s ability to modify the amount of suppression in each channel separately according to the spectral shape of the interfering sounds
A computer model of auditory efferent suppression: Implications for the recognition of speech in noise
No full textThe neural mechanisms underlying the ability of human listeners to recognize speech in the presence of background noise are still imperfectly understood. However, there is mounting evidence that the medial olivocochlear system plays an important role, via efferents that exert a suppressive effect on the response of the basilar membrane. The current paper presents a computer modeling study that investigates the possible role of this activity on speech intelligibility in noise. A model of auditory efferent processing [ Ferry, R. T., and Meddis, R. (2007). J. Acoust. Soc. Am. 122, 3519?3526 ] is used to provide acoustic features for a statistical automatic speech recognition system, thus allowing the effects of efferent activity on speech intelligibility to be quantified. Performance of the ?basic? model (without efferent activity) on a connected digit recognition task is good when the speech is uncorrupted by noise but falls when noise is present. However, recognition performance is much improved when efferent activity is applied. Furthermore, optimal performance is obtained when the amount of efferent activity is proportional to the noise level. The results obtained are consistent with the suggestion that efferent suppression causes a ?release from adaptation? in the auditory-nerve response to noisy speech, which enhances its intelligibility
Objective measures of auditory scene analysis
No full textWe describe objective measures of two aspects of auditory scene analysis (ASA). We show that the build-up of auditory streaming can be measured using a behavioural task - detection of a temporal shift of one tone relative to another - that is easiest when the two tones are part of the same stream. This paradigm is used to show that performance can be improved by requiring participants to briefly divert their attention away from the tones, a manipulation that has previously been shown to increase the number of “one stream” judgements in a subjective task. A physiological measure of streaming build-up is also obtained using the mismatch negativity paradigm. In contrast to the strong effects of attention on streaming, we show, using fMRI measures of the brain response to veridical and illusory vowels, that the continuity illusion does not depend strongly on attention
Objective measures of auditory scene analysis
No full textWe describe objective measures of two aspects of auditory scene analysis (ASA). We show that the build-up of auditory streaming can be measured using a behavioural task - detection of a temporal shift of one tone relative to another - that is easiest when the two tones are part of the same stream. This paradigm is used to show that performance can be improved by requiring participants to briefly divert their attention away from the tones, a manipulation that has previously been shown to increase the number of “one stream” judgements in a subjective task. A physiological measure of streaming build-up is also obtained using the mismatch negativity paradigm. In contrast to the strong effects of attention on streaming, we show, using fMRI measures of the brain response to veridical and illusory vowels, that the continuity illusion does not depend strongly on attention
Lateralization of Tone Complexes in Noise: The Role of Monaural Envelope Processing in Binaural Hearing
No full textThe lateralization of tone complexes presented against a diotic band-pass noise background was measured as a function of level and Interaural Time Difference (ITD) of the tone complex. The bandwidths of the sine-phase tone complex and the noise were 600 Hz, centered at 550 Hz, the component spacing of the tones was 20 Hz. Due to this spectral configuration, none of the tonal components is spectrally resolved, and the binaural cues of the combined stimulus vary with the 20 Hz cycle of the stimulus. Results show that listeners can judge the lateral position of the tone complex down to levels of -5 dB SNR. A second experiment determined masked thresholds of the tone complex in the diotic noise as a function of ITD. Detection thresholds are as low as -20 dB SNR for ITDs of 0.7 ms, and about -7 dB for ITDs of 0 ms, a condition in which only monaural information could be used by the listeners. It seems that despite the audibility of the tone complex at rather low levels (-20 dB SNR) based on binaural cues, the ability to lateralize requires the audibility of monaural envelope information, which is restricted to levels above about -7 dB SNR. Thus, monaural envelope information may be a prerequisite for the readout of lateralization information corresponding to the tone complex from the binaural display
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The auditory fovea of the barn owl - no correlation with enhanced frequency resolution.
No full textThe barn owl (Tyto alba) is a nocturnal hunter that relies on passive acoustic localization of its prey. May specializations associated with prey localization are known at all levels of the auditory system (e.g. Konishi, 1993). A striking feature of the barn owl's cochlea or basilar papilla is the highly unusual distribution of frequencies along the epithelium. In contrast to the common pattern of approximately equal lengths of the cochlea devoted to each octave (e.g. Greenwood, 1990), the barn owl provides a rapidly increasing amount of space for frequencies above 2 kHz. More than half of the basilar papilla's length is devoted to the narrow band between 5 and 10 kHz (Köppl et al., 1993). In analogy to similar cases of cochlear spatial overrepresentation in several mammals (Kössl and Vater, 1985; Vater et al., 1985; Müller et al., 1992), this has been termed an auditory fovea.
In the horseshoe and mustached bats, such foveal representations of certain narrow frequency ranges are partly accompanied by a dramatic increase in frequency resolution, that is seen in neural tuning (Suga et al., 1976; Kössl and Vater, 1990), in the generation and suppression of otoacoustic emissions (Kössl, 1994; Frank and Kössl, 1995) and in psychophysical measures of frequency selectivity (Long, 1980). This is consistent with models attributing psychophysical measures of frequency selectivity to the spatial representation of frequencies along the cochlea, such as the equal-distance hypothesis (review in Greenwood, 1991).
We investigated whether, in the barn owl, a correlation between frequency selectivity and cochlear spatial representation is present. Frequency selectivity was evaluated at the level of the basilar papilla and auditory nerve, as well as psychophysically. If a relationship with spatial representation exists, the cochlear map predicts that frequency filter bandwidths should first rise about two-fold from the lowest frequencies towards 4 kHz and then drop sharply towards 10 kHz
Subcomponent cues in binaural unmasking
No full textThe roles of fluctuations in interaural amplitude and phase in binaural unmasking were separated experimentally and examined as a function of frequency. Narrow bands of noise (1 ERB wide) with a range of centre frequencies (250-1,500 Hz) and of 500-ms duration were sinusoidally modulated at 20 Hz using either amplitude or quasi-frequency modulation (AM or QFM). In a two-interval, forced-choice task, modulation was applied in both intervals, interaurally out of phase in the signal interval and in phase in the non-signal interval. To emulate a narrow-band binaural unmasking task, the bands were used in isolation. To emulate a broadband unmasking task, flanking bands of diotic noise were added, but separated from the target band by 1-ERB-wide notches. Discrimination thresholds for narrowband AM were roughly constant as a function of frequency. However, AM with flanking bands displayed higher thresholds that increased with frequency, suggesting the presence of a cross-frequency interference effect. QFM produced a quite different data pattern, suggesting the operation of a different mechanism. Thresholds were lower than for AM up to 500 Hz, but increased sharply with frequency, and there was no effect of the flanking bands
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