Negative-delay sources in distortion product otoacoustic emissions

Publication date: Available online 22 December 2017
Source:Hearing Research
Author(s): Renata Sisto, Christopher A. Shera, Arturo Moleti
Long-delay components showing a symmetrical pattern with positive and negative delays can be observed in the time-frequency representation (or in the inverse Fourier transform) of distortion product otoacoustic emissions. Positive-only phase-gradient delays are predicted by place-fixed backscattering mechanisms, such as coherent reflection due to roughness, whereas the nonlinear distortion wave-fixed mechanism should generate an almost null-delay component. The symmetrical delay pattern arises whenever spectral amplitude fluctuations are not fully correlated to phase fluctuations. An interpretation of this phenomenon is proposed, involving place-fixed modulation of the spectral strength of the wave–fixed nonlinear generator.Experimental data are shown in which these negative-delay sources are particularly strong, and further amplified by contralateral stimulation, suggesting that this effect could be dynamically enhanced. Analytical solutions of a linear 1-d transmission line model, in which cubic nonlinearity and roughness were added as small perturbations, have been used to test this hypothesis.



from #Audiology via ola Kala on Inoreader http://ift.tt/2kWQWfW
via IFTTT

Intentional switching in auditory selective attention: Exploring attention shifts with different reverberation times

Publication date: Available online 22 December 2017
Source:Hearing Research
Author(s): Josefa Oberem, Julia Seibold, Iring Koch, Janina Fels
Using a well-established binaural-listening paradigm the ability to intentionally switch auditory selective attention was examined under anechoic, low reverberation (0.8 s) and high reverberation (1.75 s) conditions. Twenty-three young, normal-hearing subjects were tested in a within-subject design to analyze influences of the reverberation times. Spoken word pairs by two speakers were presented simultaneously to subjects from two of eight azimuth positions. The stimuli consisted of a single number word, (i.e., 1 to 9), followed by either the direction “UP” or “DOWN” in German. Guided by a visual cue prior to auditory stimulus onset indicating the position of the target speaker, subjects were asked to identify whether the target number was numerically smaller or greater than five and to categorize the direction of the second word. Switch costs, (i.e. reaction time differences between a position switch of the target relative to a position repetition), were larger under the high reverberation condition. Furthermore, the error rates were highly dependent on reverberant energy and reverberation interacted with the congruence effect, (i.e. stimuli spoken by target and distractor may evoke the same answer (congruent) or different answers (incongruent)), indicating larger congruence effects under higher reverberation times.



from #Audiology via ola Kala on Inoreader http://ift.tt/2kDyucD
via IFTTT

Olivocochlear Efferents: Their action, effects, measurement and uses, and the impact of the new conception of cochlear mechanical responses

Publication date: Available online 21 December 2017
Source:Hearing Research
Author(s): John J. Guinan
The anatomy and physiology of olivocochlear (OC) efferents are reviewed. To help interpret these, recent advances in cochlear mechanics are also reviewed. Lateral OC (LOC) efferents innervate primary auditory-nerve (AN) fiber dendrites. The most important LOC function may be to reduce auditory neuropathy. Medial OC (MOC) efferents innervate the outer hair cells (OHCs) and act to turn down the gain of cochlear amplification. Cochlear amplification had been thought to act only through basilar membrane (BM) motion, but recent reports show that motion near the reticular lamina (RL) is amplified more than BM motion, and that RL-motion amplification extends to several octaves below the local characteristic frequency. Data on efferent effects on AN-fiber responses, otoacoustic emissions (OAEs) and human psychophysics are reviewed and reinterpreted in the light of the new cochlear-mechanical data. The possible origin of OAEs in RL motion is considered. MOC-effect measuring methods and MOC-induced changes in human responses are also reviewed, including that ipsilateral and contralateral sound can produce MOC effects with different patterns across frequency. MOC efferents help to reduce damage due to acoustic trauma. Many, but not all, reports show that subjects with stronger contralaterally-evoked MOC effects have better ability to detect signals (e.g. speech) in noise, and that MOC effects can be modulated by attention.



from #Audiology via ola Kala on Inoreader http://ift.tt/2kXngPN
via IFTTT

Talker Differences in Clear and Conversational Speech: Perceived Sentence Clarity for Young Adults With Normal Hearing and Older Adults With Hearing Loss

Purpose

The purpose of this study is to examine talker differences for subjectively rated speech clarity in clear versus conversational speech, to determine whether ratings differ for young adults with normal hearing (YNH listeners) and older adults with hearing impairment (OHI listeners), and to explore effects of certain talker characteristics (e.g., gender) on perceived clarity. Relationships among clarity ratings and other speech perceptual and acoustic measures were also explored.

Method

Twenty-one YNH and 15 OHI listeners rated clear and conversational sentences produced by 41 talkers on a scale of 1 (lowest possible clarity) to 7 (highest possible clarity).

Results

While clarity ratings varied significantly among talkers, listeners rated clear speech significantly clearer than conversational speech for all but 1 talker. OHI and YNH listeners gave similar ratings for conversational speech, but ratings for clear speech were significantly higher for OHI listeners. Talker gender effects differed for YNH and OHI listeners. Ratings of clear speech varied among subgroups of talkers with different amounts of experience talking to people with hearing loss.

Conclusions

Perceived clarity varies widely among talkers, but nearly all produce clear speech that sounds significantly clearer than their conversational speech. Few differences were seen between OHI and YNH listeners except the effect of talker gender.

from #Audiology via ola Kala on Inoreader http://ift.tt/2kAuyt8
via IFTTT

Talker Differences in Clear and Conversational Speech: Perceived Sentence Clarity for Young Adults With Normal Hearing and Older Adults With Hearing Loss

Purpose

The purpose of this study is to examine talker differences for subjectively rated speech clarity in clear versus conversational speech, to determine whether ratings differ for young adults with normal hearing (YNH listeners) and older adults with hearing impairment (OHI listeners), and to explore effects of certain talker characteristics (e.g., gender) on perceived clarity. Relationships among clarity ratings and other speech perceptual and acoustic measures were also explored.

Method

Twenty-one YNH and 15 OHI listeners rated clear and conversational sentences produced by 41 talkers on a scale of 1 (lowest possible clarity) to 7 (highest possible clarity).

Results

While clarity ratings varied significantly among talkers, listeners rated clear speech significantly clearer than conversational speech for all but 1 talker. OHI and YNH listeners gave similar ratings for conversational speech, but ratings for clear speech were significantly higher for OHI listeners. Talker gender effects differed for YNH and OHI listeners. Ratings of clear speech varied among subgroups of talkers with different amounts of experience talking to people with hearing loss.

Conclusions

Perceived clarity varies widely among talkers, but nearly all produce clear speech that sounds significantly clearer than their conversational speech. Few differences were seen between OHI and YNH listeners except the effect of talker gender.

from #Audiology via xlomafota13 on Inoreader http://ift.tt/2kAuyt8
via IFTTT

Talker Differences in Clear and Conversational Speech: Perceived Sentence Clarity for Young Adults With Normal Hearing and Older Adults With Hearing Loss

Purpose

The purpose of this study is to examine talker differences for subjectively rated speech clarity in clear versus conversational speech, to determine whether ratings differ for young adults with normal hearing (YNH listeners) and older adults with hearing impairment (OHI listeners), and to explore effects of certain talker characteristics (e.g., gender) on perceived clarity. Relationships among clarity ratings and other speech perceptual and acoustic measures were also explored.

Method

Twenty-one YNH and 15 OHI listeners rated clear and conversational sentences produced by 41 talkers on a scale of 1 (lowest possible clarity) to 7 (highest possible clarity).

Results

While clarity ratings varied significantly among talkers, listeners rated clear speech significantly clearer than conversational speech for all but 1 talker. OHI and YNH listeners gave similar ratings for conversational speech, but ratings for clear speech were significantly higher for OHI listeners. Talker gender effects differed for YNH and OHI listeners. Ratings of clear speech varied among subgroups of talkers with different amounts of experience talking to people with hearing loss.

Conclusions

Perceived clarity varies widely among talkers, but nearly all produce clear speech that sounds significantly clearer than their conversational speech. Few differences were seen between OHI and YNH listeners except the effect of talker gender.

from #Audiology via ola Kala on Inoreader http://ift.tt/2kAuyt8
via IFTTT

Immune cells and non-immune cells with immune function in mammalian cochleae

Publication date: Available online 20 December 2017
Source:Hearing Research
Author(s): Bo Hua Hu, Celia Zhang, Mitchell D. Frye
The cochlea has an immune environment dominated by macrophages under resting conditions. When stressed, circulating monocytes enter the cochlea. These immune mediators, along with cochlear resident cells, organize a complex defense response against pathological challenges. Since the cochlea has minimal exposure to pathogens, most inflammatory conditions in the cochlea are sterile. Although the immune response is initiated for the protection of the cochlea, off-target effects can cause collateral damage to cochlear cells. A better understanding of cochlear immune capacity and regulation would therefore lead to development of new therapeutic treatments. Over the past decade, there have been many advances in our understanding of cochlear immune capacity. In this review, we provide an update and overview of the cellular components of cochlear immune capacity with a focus on macrophages in mammalian cochleae. We describe the composition and distribution of immune cells in the cochlea and suggest that phenotypic and functional characteristics of macrophages have site-specific diversity. We also highlight the response of immune cells to acute and chronic stresses and comment on the potential function of immune cells in cochlear homeostasis and disease development. Finally, we briefly review potential roles for cochlear resident cells in the immune activities of the cochlea.



from #Audiology via ola Kala on Inoreader http://ift.tt/2kxbSeb
via IFTTT