Relevance of the Implementation of Teeth in Three-Dimensional Vocal Tract Models

Purpose

Recently, efforts have been made to investigate the vocal tract using magnetic resonance imaging (MRI). Due to technical limitations, teeth were omitted in many previous studies on vocal tract acoustics. However, the knowledge of how teeth influence vocal tract acoustics might be important in order to estimate the necessity of implementing teeth in vocal tract models. The aim of this study was therefore to estimate the effect of teeth on vocal tract acoustics.

Method

The acoustic properties of 18 solid (3-dimensional printed) vocal tract models without teeth were compared to the same 18 models including teeth in terms of resonance frequencies (f _Rn). The f _Rn were obtained from the transfer functions of these models excited by white noise at the glottis level. The models were derived from MRI data of 2 trained singers performing 3 different vowel conditions (/i/, /a/, and /u/) in speech and low-pitched and high-pitched singing.

Results

Depending on the oral configuration, models exhibiting side cavities or side branches were characterized by major changes in the transfer function when teeth were implemented via the introduction of pole-zero pairs.

Conclusions

To avoid errors in modeling, teeth should be included in 3-dimensional vocal tract models for acoustic evaluation.

Supplemental Material

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Relevance of the Implementation of Teeth in Three-Dimensional Vocal Tract Models

Purpose

Recently, efforts have been made to investigate the vocal tract using magnetic resonance imaging (MRI). Due to technical limitations, teeth were omitted in many previous studies on vocal tract acoustics. However, the knowledge of how teeth influence vocal tract acoustics might be important in order to estimate the necessity of implementing teeth in vocal tract models. The aim of this study was therefore to estimate the effect of teeth on vocal tract acoustics.

Method

The acoustic properties of 18 solid (3-dimensional printed) vocal tract models without teeth were compared to the same 18 models including teeth in terms of resonance frequencies (f _Rn). The f _Rn were obtained from the transfer functions of these models excited by white noise at the glottis level. The models were derived from MRI data of 2 trained singers performing 3 different vowel conditions (/i/, /a/, and /u/) in speech and low-pitched and high-pitched singing.

Results

Depending on the oral configuration, models exhibiting side cavities or side branches were characterized by major changes in the transfer function when teeth were implemented via the introduction of pole-zero pairs.

Conclusions

To avoid errors in modeling, teeth should be included in 3-dimensional vocal tract models for acoustic evaluation.

Supplemental Material

http://ift.tt/2wnkzL9

from #Audiology via ola Kala on Inoreader http://article/doi/10.1044/2017_JSLHR-S-16-0395/2654188/Relevance-of-the-Implementation-of-Teeth-in
via IFTTT

Relevance of the Implementation of Teeth in Three-Dimensional Vocal Tract Models

Purpose

Recently, efforts have been made to investigate the vocal tract using magnetic resonance imaging (MRI). Due to technical limitations, teeth were omitted in many previous studies on vocal tract acoustics. However, the knowledge of how teeth influence vocal tract acoustics might be important in order to estimate the necessity of implementing teeth in vocal tract models. The aim of this study was therefore to estimate the effect of teeth on vocal tract acoustics.

Method

The acoustic properties of 18 solid (3-dimensional printed) vocal tract models without teeth were compared to the same 18 models including teeth in terms of resonance frequencies (f _Rn). The f _Rn were obtained from the transfer functions of these models excited by white noise at the glottis level. The models were derived from MRI data of 2 trained singers performing 3 different vowel conditions (/i/, /a/, and /u/) in speech and low-pitched and high-pitched singing.

Results

Depending on the oral configuration, models exhibiting side cavities or side branches were characterized by major changes in the transfer function when teeth were implemented via the introduction of pole-zero pairs.

Conclusions

To avoid errors in modeling, teeth should be included in 3-dimensional vocal tract models for acoustic evaluation.

Supplemental Material

http://ift.tt/2wnkzL9

from #Audiology via xlomafota13 on Inoreader http://article/doi/10.1044/2017_JSLHR-S-16-0395/2654188/Relevance-of-the-Implementation-of-Teeth-in
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Amplitude modulation rate dependent topographic organization of the auditory steady-state response in human auditory cortex

Publication date: Available online 11 September 2017
Source:Hearing Research
Author(s): Nathan Weisz, Chrysoula Lithari
Periodic modulations of an acoustic feature, such as amplitude over a certain frequency range, leads to phase locking of neural responses to the envelope of the modulation. Using electrophysiological methods this neural activity pattern, also called the auditory steady-state response (aSSR), is visible following frequency transformation of the evoked response as a clear spectral peak at the modulation frequency. Despite several studies employing the aSSR that show, for example, strongest responses for ∼40 Hz and an overall right-hemispheric dominance, it has not been investigated so far to what extent within auditory cortex different modulation frequencies elicit aSSRs at a homogenous source or whether the localization of the aSSR is topographically organized in a systematic manner. The latter would be suggested by previous neuroimaging works in monkeys and humans showing a periodotopic organization within and across distinct auditory fields. However, the sluggishness of the signal from these neuroimaging works prohibit inferences with regards to the fine-temporal features of the neural response. In the present study, we employed amplitude-modulated (AM) sounds over a range between 4 and 85 Hz to elicit aSSRs while recording brain activity via magnetoencephalography (MEG). Using beamforming and a fine spatially resolved grid restricted to auditory cortical processing regions, our study revealed a topographic representation of the aSSR that depends on AM rate, in particular in the medial-lateral (bilateral) and posterior-anterior (right auditory cortex) direction. In summary, our findings confirm previous studies that showing different AM rates to elicit maximal response in distinct neural populations. They extend these findings however by also showing that these respective neural ensembles in auditory cortex actually phase lock their activity over a wide modulation frequency range.



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A methodological assessment of studies that use voxel based morphometry to study neural changes in tinnitus patients

Publication date: Available online 11 September 2017
Source:Hearing Research
Author(s): Nicholas Scott-Wittenborn, Omar A. Karadaghy, Jay F. Piccirillo, Jonathan E. Peelle
BackgroundThe scientific understanding of tinnitus and its etiology have transitioned from thinking of tinnitus as solely a peripheral auditory problem to an increasing awareness that cortical networks may play a critical role in tinnitus percept or bother. With this change, studies that seek to use structural brain imaging techniques to better characterize tinnitus patients have become more common. These studies include using voxel-based morphometry (VBM) to determine if there are differences in regional gray matter volume in individuals who suffer from tinnitus and those who do not. However, studies using VBM in patients with tinnitus have produced inconsistent and sometimes contradictory results.ObjectiveThis paper is a systematic review of all of the studies to date that have used VBM to study regional gray matter volume in people with tinnitus, and explores ways in which methodological differences in these studies may account for their heterogeneous results. We also aim to provide guidance on how to conduct future studies using VBM to produce more reproducible results to further our understanding of disease processes such as tinnitus.MethodsStudies about tinnitus and VBM were searched for using PubMed and Embase. These returned 15 and 25 results respectively. Of these, nine met the study criteria and were included for review. An additional 5 studies were identified in the literature as pertinent to the topic at hand and were added to the review, for a total of 13 studies.ResultsThere was significant heterogeneity among the studies in several areas, including inclusion and exclusion criteria, software programs, and statistical analysis. We were not able to find publicly shared data or code for any study.DiscussionThe differences in study design, software analysis, and statistical methodology make direct comparisons between the different studies difficult. Especially problematic are the differences in the inclusion and exclusion criteria of the study, and the statistical design of the studies, both of which could radically alter findings. Thus, heterogeneity has complicated efforts to explore the etiology of tinnitus using structural MRI.ConclusionThere is a pressing need to standardize the use of VBM when evaluating tinnitus patients. While some heterogeneity is expected given the rapid advances in the field, more can be done to ensure that there is internal validity between studies.



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Severe streptomycin ototoxicity in the mouse utricle leads to a flat epithelium but the peripheral neural degeneration is delayed

Publication date: Available online 11 September 2017
Source:Hearing Research
Author(s): Guo-Peng Wang, Ishani Basu, Lisa A. Beyer, Hiu Tung Wong, Donald L. Swiderski, Shu-Sheng Gong, Yehoash Raphael
The damaged vestibular sensory epithelium of mammals has a limited capacity for spontaneous hair cell regeneration, which largely depends on the transdifferentiation of surviving supporting cells. Little is known about the response of vestibular supporting cells to a severe insult. In the present study, we evaluated the impact of a severe ototoxic insult on the histology of utricular supporting cells and the changes in innervation that ensued. We infused a high dose of streptomycin into the mouse posterior semicircular canal to induce a severe lesion in the utricle. Both scanning electron microscopy and light microscopy of plastic sections showed replacement of the normal cytoarchitecture of the epithelial layer with a flat layer of cells in most of the samples. Immunofluorescence staining showed numerous cells in the severely damaged epithelial layer that were negative for hair cell and supporting cell markers. Nerve fibers under the flat epithelium had high density at the 1 month time point but very low density by 3 months. Similarly, the number of vestibular ganglion neurons was unchanged at 1 month after the lesion, but was significantly lower at 3 months. We therefore determined that the mouse utricular epithelium turns into a flat epithelium after a severe lesion, but the degeneration of neural components is slow, suggesting that treatments to restore balance by hair cell regeneration, stem cell therapy or vestibular prosthesis implantation will likely benefit from the short term preservation of the neural substrate.



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Facilitation and refractoriness of the electrically evoked compound action potential

Publication date: Available online 11 September 2017
Source:Hearing Research
Author(s): Matthias Hey, Joachim Müller-Deile, Horst Hessel, Matthijs Killian
In this study we aim to resolve the contributions of facilitation and refractoriness at very short pulse intervals. Measurements of the refractory properties of the electrically evoked compound action potential (ECAP) of the auditory nerve in cochlear implant (CI) users at inter pulse intervals below 300 μs are influenced by facilitation and recovery effects. ECAPs were recorded using masker pulses with a wide range of current levels relative to the probe pulse levels, for three suprathreshold probe levels and pulse intervals of 13 … 200 μs. Evoked potentials were measured for 21 CI patients by using the masked response extraction artifact cancellation procedure.During analysis of the measurements the stimulation current was not used as absolute value, but in relation to the patient's individual ECAP threshold. This enabled a more general approach to describe facilitation as a probe level independent effect. Maximum facilitation was found for all tested inter pulse intervals at masker levels near patient's individual ECAP threshold, independent from probe level. For short inter pulse intervals an increased N1P1 amplitude was measured for subthreshold masker levels down to 120 CL below patient's individual ECAP threshold in contrast to the recreated state.ECAPs recorded with inter pulse intervals up to 200 μs are influenced by facilitation and recovery. Facilitation effects are most pronounced for masker levels at or below ECAP threshold, while recovery effects increase with higher masker levels above ECAP threshold. The local maximum of the ECAP amplitude for masker levels around ECAP threshold can be explained by the mutual influence of maximum facilitation and minimal refractoriness.



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