1,721,152 research outputs found
Simple models; complex flows
No full textIntroduction: Advances in computational fluid dynamic (CFD) modelling allow ever more sophisticated models of the fluid flow in the larynx to be produced (e.g. Horá?ek and Gráf, 2009). More recently, the ability to couple models between multiple physical domains has allowed fluid models to interact with dynamic tissue models and/or with models of acoustic generation (e.g. Zörner et al., 2009). The ability to model abrupt features, both temporal (such as glottal closure) and spatial (such large area changes) is less well developed. It is interesting to explore the effect that small geometric changes may have on a flow field and its sound generating properties to try to evaluate the sensitivity of speech flow regimes to approximations in the channel shape.Methods: Measurements made on a dynamic mechanical model of the vocal folds and tract (Barney and Jackson, 2009) have been used to investigate the sensitivity of the hydrodynamic and acoustic fields to small changes in the tract geometry. Pressure at the duct wall in the model vocal tract and radiated SPL at the model lips were measured while an oscillating flow interacted with an orifice plate and a down-stream obstacle. The effect of small changes in the relative location of the geometric features on the fluid behaviour and acoustic output was observed.Results: The interaction between the fluid motion and the geometric features was highly dependent on their relative configuration, with a corresponding sensitive dependence regarding the generation of sound. Complex interactions between the fields developed from relatively simple structural combinations.Discussion: When modelling flow regimes within the larynx and vocal tract we need to be aware that even slight approximations in the geometric specification of the duct can have significant and complex effects on the hydrodynamic and acoustic fields and their interaction. Comparison of outputs from CFD models where duct geometries are an approximation to the real shape with the fluid behaviour in the in vivo vocal tract is therefore challenging. Rather than looking for absolute models of flow fields, a more productive paradigm may be to use CFD models to answer specific questions about the effect of geometric change on the flow and acoustic fields and their interaction.<br/
Dynamic mechanical modelling of speech
No full textIn voiced speech, the source of sound is the vibrations of the vocal folds within the larynx. The steady flow of air passing out from the lungs is modulated by a complex fluid-tissue interaction in the larynx and excites acoustically the vocal tract downstream of the glottal exit. The system is small and inaccessible and, being situated inside a living person, is unsuitable for many kinds of experimentation. In vitro models offer the opportunity for systematic empirical studies in a controllable environment. This paper describes experimental measurements of the flow and pressure regimes made on a driven mechanical model of the vocal folds and vocal tract. The model has been used in a range of studies to explore jet formation and development downstream from the glottal exit, the effect of small changes in the duct geometry and, latterly, the interrelationship between the vibrating glottal source and a noise source further downstream as found in voiced fricative sounds
Fluid flow in a dynamic mechanical model of the larynx
No full textA dynamic mechanical model of the human larynx and vocal tract has been developed to investigate its acoustic and fluid dynamic behaviour during sustained vowel production. The model comprises a cylindrical duct, open at one end, with a controlled air flow introduced at the other. The flow entering the duct is modulated by the periodic opening and closing of pair of electro-mechanically driven shutters. Far field measurements of the radiated pressure have shown that the model generates sound which has a spectral distribution that corresponds, at low frequencies, to that of an open vowel. However the spectral amplitudes were somewhat lower than voiced speech sounds normally generated at the same low rate. The addition of an orifice plate to reduce the duct exit area was found to increase the level of the radiated sound and to modify the spectral distribution somewhat. The flow distribution throughout the model duct has been measured using hot wire anemometry. The velocity distribution measured in the model was found to correspond to that measured in the oral cavity of four live subjects. Calibrate pressure measurements at the duct wall have been used define the associated pressure field within the duct. The pressure distribution found within the model corresponded to that measured in vivo by other researchers. The velocity within the duct was shown to be associated with contributions from three separate velocity fields, the rotational acoustic particle velocity and a rotational velocity field due to vortex development at the exit to the shutters. It was shown that the rotational velocity disturbance convected along the duct at approximately the local mean flow velocity. Comparison of prediction with measurement of the radiated sound fields showed that the presence of a rotational velocity field at the duct exit made a significant contribution to the radiated sound pressure level. A discussion is included as to whether acoustic sources, associated with the rotational flow, exists at area discontinuities in the vocal tract in addition to the generally accepted acoustic source due to fluctuating mass flow at the glottal exit. The influence of the Rotheberg Mask on the flow and acoustic behaviour of the model was investigated in some detail. Measurements show that the velocity field was almost unaltered, but the fluctuating pressure amplitudes were greatly reduced. Corresponding reductions were found in the radiated acoustic power with further reductions apparently due to the suppression of the rotational flow sources by the mask
Clinical criteria for benign laryngeal mucosal evaluation and treatment, including evidence based assessment of voice
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Aerodynamic measures of speech in unilateral vocal fold paralysis (UVFP) patients
No full textThis paper reports the recording and analysis of an aerodynamic database of 51 words produced by four patients with Unilateral Vocal Fold Paralysis. The vowel-fricative-vowel boundaries were manually annotated and the mean absolute oral airflow amplitude (OA), fundamental frequency (f0) and first formant intensity (IF1) were extracted from a 20 ms window in the steady state of each phone. A case study approach to analysis of phonatory behaviour for the subjects is presented.Significant differences were found between the absolute OA and IF1 for different phones. Large between subject variations in absolute measures for OA and f0 were found. Relative values calculated from the difference in these parameters between phones show consistency for subjects of the same gender. <br/
Computer aided lung sound analysis: a preliminary study to assess its potential as a new outcome measure for respiratory therapy
No full textA barrier to assess the relative effectiveness of respiratory therapies has been insufficient accurate, reliable, and sensitive outcome measures. Lung sounds provide useful information for assessing and monitoring respiratory patients. However, standard auscultation is too subjective to allow them to be used as an outcome measure. In this paper, Computer Aided Lung Sound Analysis (CALSA) characterising crackles’ Initial Deflection Width (IDW) and Two Cycle Deflection (2CD) is proposed as a potentialobjective, non-invasive, bedside outcome measure to assess the response to alveolar recruitment and airwayclearance interventions. A preliminary ‘repeated measures’ experimental study was conducted. Seventeenparticipants with cystic fibrosis were recruited from out-patient clinics. Demographic, anthropometric and lung sound data were collected. The intra-subject reliability of crackles’ IDW and 2CD was found to be ‘good’ to ‘excellent’, estimated by the Analysis of Variance, Intraclass Correlation Coefficient, Bland and Altman 95% limits of agreement and Smallest Real Difference. It is concluded that crackle IDW and 2CD detected by CALSA are reliable and stable measures. In future, CALSA may be useful for assessing and monitoring respiratory interventions in clinical settings
The presence of a female influences courtship performance of male manakins
No full textCoordinated courtship displays are a common feature of species forming long-term pair bonds. In lekking species, on the contrary, there are no stable pair bonds because partners meet only to copulate, and males indicate their quality and/or attractiveness to females by displaying morphological and behavioral traits. In some cases, females interact with these displaying males, but little is known about the role of the females in these encounters. In the Neotropical bearded manakins, females join males in their acrobatic courtship displays in the final phase of mate choice. We hypothesize that females participate in the courtship dance to better assess male motor skill by observing male responses to female signals. We filmed at high speed the courtship displays of 2 species of bearded manakins and compared the displays performed by males alone, where the female is absent from the arena, with those performed together with a female. In addition, we compared the movements of the male with those of the female and analyzed the display coordination. We found that when a female is present in the arena, males increase the speed or frequency of several performance parameters that are strongly correlated with courtship success. Additionally, males seem to pace their movements to those of the female as she takes the lead in the duo dance. Our results suggest that before choosing a mate for copulation, female manakins challenge the motor skills of prospective males. © 2015 American Ornithologists' Union
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