23 research outputs found
Experimental investigation of multiphase flow and acoustics during voice production
No full textThis dissertation advances the understanding of human phonation by integrating biomechanical modeling, aerosol analysis, and acoustic evaluation in a single comprehensive framework. First, a biomimetic, multi-layered synthetic larynx model was developed to replicate key features of human vocal fold physiology. By embedding ligament fibers with varying diameters and tensile strengths, the model allows controlled posturing (elongation, abduction, adduction) and dynamic manipulation of vocal fold stiffness. Systematic experiments revealed that increased fiber tension raises fundamental frequency and subglottal pressure, closely mirroring physiological observations of pitch regulation and providing a robust platform for studying both healthy and pathological voice conditions.
In a second step, the thesis elucidates aerosol formation mechanisms during phonation by combining the synthetic larynx model with synthetic mucus formulations that replicate human laryngeal mucus properties. Detailed high-speed imaging and particle image velocimetry showed that reduced surface tension and increased airflow reinforce aerosol particle generation, emphasizing the influence of mucus rheology and vocal fold dynamics on droplet release at the glottal level. These findings have direct implications for understanding transmission risks of airborne pathogens during speech and singing.
Finally, the acoustic effects of professional singing masks were investigated to reconcile infection control measures with vocal performance demands. Tests on a KEMAR head phantom demonstrated that although specialized fabrics and plastic face shields can mitigate frontal aerosol dispersion, they also introduce measurable spectral filtering of the acoustics, especially at higher frequencies. Some designs additionally cause low frequency amplification or altered directional radiation, potentially compromising vocal quality and clarity.
Collectively, this work integrates advanced physical modeling of physiological vocal fold oscillation with applied aerosol dispersion during phonation and the impact on the resulting acoustics. The outcomes not only enhance fundamental knowledge of vocal fold biomechanics but also support evidence-based strategies for safeguarding public health improving vocal performance in professional and educational settings, as well as addressing clinical needs.Diese Dissertation erweitert das Verständnis der menschlichen Stimmgebung, indem sie biomechanische Modellierung, Aerosolgenerierung und -ausbreitung und akustische Untersuchungen in einem umfassenden Forschungsansatz vereint. Zunächst wurde ein biomimetisches, mehrschichtiges synthetisches Larynxmodell entwickelt, das zentrale Aspekte der menschlichen Stimmlippenphysiologie abbildet. Durch die Integration von Ligamentfasern unterschiedlicher Durchmesser und Zugfestigkeiten ermöglicht das Modell eine gezielte Veränderung von Elongation, Adduktion und Abduktion sowie eine dynamische Anpassung der Steifigkeit der Stimmlippen. Systematische Experimente zeigten, dass eine höhere Faserspannung sowohl die Grundfrequenz als auch den subglottalen Druck erhöht und somit die menschliche Stimmgebung realistisch nachbildet. Damit bietet das Modell eine robuste Plattform, um gesunde und pathologische Zustände der Phonation zu untersuchen.
Im zweiten Schritt beleuchtet die Arbeit die Entstehung von Aerosolen während der Phonation, indem das synthetische Larynxmodell mit synthetischem Mukus kombiniert wurde, der die viskoelastischen Eigenschaften von menschlichem laryngealen Mukus nachahmt. High-speed Videoaufzeichnungen der Stimmlippenschwingung und Strömungsvisualisierung im supraglottalen Bereich zeigen, dass eine verringerte Oberflächenspannung des Mukus und ein erhöhter Luftstrom die Bildung von Aerosolpartikeln verstärken. Dies unterstreicht den Einfluss der Mukusrheologie und Stimmlippendynamik auf die Partikelentstehung auf glottaler Ebene und liefert wertvolle Erkenntnisse für die Bewertung von Infektionsrisiken bei Sprech- und Gesangstätigkeiten.
Abschlie\ss end wurden die akustischen Auswirkungen professioneller Sängermasken untersucht, um Infektionsschutzmaß nahmen mit den Anforderungen an die stimmliche Lei\-stungsfähigkeit zu vereinen. Versuche an einem KEMAR-Kopf belegten, dass spezielle Stoffe und transparente Kunststoffe zwar den frontalen Aerosolausstoß reduzieren, jedoch gleichzeitig deutlich hörbare akustische Filtereffekte, insbesondere bei hohen Frequenzen, hervorrufen. Zusätzlich können bestimmte Maskentypen zu einer Verstärkung tiefer Frequenzen oder einer veränderten räumlichen Schallabstrahlung führen und damit Klangqualität und Verständlichkeit beeinträchtigen.
Zusammenfassend vereint diese Arbeit die physikalische Modellierung physiologischer Stimmlippenschwingungen mit der praxisnahen Untersuchung von Aerosolausbreitung während der Phonation und den Einfluss auf die resultierende Akustik beim Tragen von Masken, um die Ausbreitung von Aerosolen zu reduzieren. Die Ergebnisse tragen nicht nur zu einem vertieften Grundlagenverständnis der Biomechanik der Stimmlippen bei, sondern unterstützen auch evidenzbasierte Strategien zum Schutz der öffentlichen Gesundheit, zur Verbesserung der stimmlichen Leistungsfähigkeit in beruflichen und pädagogischen Kontexten sowie zu Optimierungen im klinischen Betrieb
Neural network-based estimation of biomechanical vocal fold parameters
No full textVocal fold (VF) vibrations are the primary source of human phonation. High-speed video (HSV) endoscopy enables the computation of descriptive VF parameters for assessment of physiological properties of laryngeal dynamics, i.e., the vibration of the VFs. However, underlying biomechanical factors responsible for physiological and disordered VF vibrations cannot be accessed. In contrast, physically based numerical VF models reveal insights into the organ’s oscillations, which remain inaccessible through endoscopy. To estimate biomechanical properties, previous research has fitted subglottal pressure-driven mass–spring–damper systems, as inverse problem to the HSV-recorded VF trajectories, by global optimization of the numerical model. A neural network trained on the numerical model may be used as a substitute for computationally expensive optimization, yielding a fast evaluating surrogate of the biomechanical inverse problem. This paper proposes a convolutional recurrent neural network (CRNN)-based architecture trained on regression of a physiological-based biomechanical six-mass model (6 MM). To compare with previous research, the underlying biomechanical factor “subglottal pressure” prediction was tested against 288 HSV ex vivo porcine recordings. The contributions of this work are two-fold: first, the presented CRNN with the 6 MM handles multiple trajectories along the VFs, which allows for investigations on local changes in VF characteristics. Second, the network was trained to reproduce further important biomechanical model parameters like VF mass and stiffness on synthetic data. Unlike in a previous work, the network in this study is therefore an entire surrogate of the inverse problem, which allowed for explicit computation of the fitted model using our approach. The presented approach achieves a best-case mean absolute error (MAE) of 133 Pa (13.9%) in subglottal pressure prediction with 76.6% correlation on experimental data and a re-estimated fundamental frequency MAE of 15.9 Hz (9.9%). In-detail training analysis revealed subglottal pressure as the most learnable parameter. With the physiological-based model design and advances in fast parameter prediction, this work is a next step in biomechanical VF model fitting and the estimation of laryngeal kinematics
Influence of flow rate and fiber tension on dynamical, mechanical and acoustical parameters in a synthetic larynx model with integrated fibers
No full textIntroductionThe human voice is generated by the oscillation of the vocal folds induced by exhalation airflow. Consequently, the characteristics of these oscillations and the primary sound signal are controlled by the longitudinal tension of the vocal folds, the flow rate, and their prephonatoric position. To facilitate independent control of these parameters, a synthetic larynx model was developed, as detailed in a previous publication.MethodsThis study aims to statistically analyze the influence of airflow and fiber tension on phonation characteristics, such as periodicity and symmetry, glottis closure during vocal fold oscillations, as well as tissue elasticity and generated sound. A total of 76 experiments were conducted and statistically analyzed with a systematic variation of flow rate and longitudinal tension within the vocal folds.During these experiments, vocal fold motion, subglottal pressure, and emitted sound were meticulously measured and analyzed.ResultsGroupwise statistical testing identified the flow rate as the main influencing parameter on nearly all phonation characteristics. However, the fundamental frequency, stiffness parameters, and quality parameters of the primary sound signal are predominantly controlled by the longitudinal tension within the vocal folds.DiscussionThe results demonstrated a complex interplay between the flow rate and tension, resulting in different characteristics of the produced sound signal
DataSheet1_Neural network-based estimation of biomechanical vocal fold parameters.PDF
No full textVocal fold (VF) vibrations are the primary source of human phonation. High-speed video (HSV) endoscopy enables the computation of descriptive VF parameters for assessment of physiological properties of laryngeal dynamics, i.e., the vibration of the VFs. However, underlying biomechanical factors responsible for physiological and disordered VF vibrations cannot be accessed. In contrast, physically based numerical VF models reveal insights into the organ’s oscillations, which remain inaccessible through endoscopy. To estimate biomechanical properties, previous research has fitted subglottal pressure-driven mass–spring–damper systems, as inverse problem to the HSV-recorded VF trajectories, by global optimization of the numerical model. A neural network trained on the numerical model may be used as a substitute for computationally expensive optimization, yielding a fast evaluating surrogate of the biomechanical inverse problem. This paper proposes a convolutional recurrent neural network (CRNN)-based architecture trained on regression of a physiological-based biomechanical six-mass model (6 MM). To compare with previous research, the underlying biomechanical factor “subglottal pressure” prediction was tested against 288 HSV ex vivo porcine recordings. The contributions of this work are two-fold: first, the presented CRNN with the 6 MM handles multiple trajectories along the VFs, which allows for investigations on local changes in VF characteristics. Second, the network was trained to reproduce further important biomechanical model parameters like VF mass and stiffness on synthetic data. Unlike in a previous work, the network in this study is therefore an entire surrogate of the inverse problem, which allowed for explicit computation of the fitted model using our approach. The presented approach achieves a best-case mean absolute error (MAE) of 133 Pa (13.9%) in subglottal pressure prediction with 76.6% correlation on experimental data and a re-estimated fundamental frequency MAE of 15.9 Hz (9.9%). In-detail training analysis revealed subglottal pressure as the most learnable parameter. With the physiological-based model design and advances in fast parameter prediction, this work is a next step in biomechanical VF model fitting and the estimation of laryngeal kinematics.</p
An Investigation of Acoustic Back-Coupling in Human Phonation on a Synthetic Larynx Model
No full textIn the human phonation process, acoustic standing waves in the vocal tract can influence the fluid flow through the glottis as well as vocal fold oscillation. To investigate the amount of acoustic back-coupling, the supraglottal flow field has been recorded via high-speed particle image velocimetry (PIV) in a synthetic larynx model for several configurations with different vocal tract lengths. Based on the obtained velocity fields, acoustic source terms were computed. Additionally, the sound radiation into the far field was recorded via microphone measurements and the vocal fold oscillation via high-speed camera recordings. The PIV measurements revealed that near a vocal tract resonance frequency fR, the vocal fold oscillation frequency fo (and therefore also the flow field’s fundamental frequency) jumps onto fR. This is accompanied by a substantial relative increase in aeroacoustic sound generation efficiency. Furthermore, the measurements show that fo-fR-coupling increases vocal efficiency, signal-to-noise ratio, harmonics-to-noise ratio and cepstral peak prominence. At the same time, the glottal volume flow needed for stable vocal fold oscillation decreases strongly. All of this results in an improved voice quality and phonation efficiency so that a person phonating with fo-fR-coupling can phonate longer and with better voice quality
Effect of Ligament Fibers on Dynamics of Synthetic, Self-Oscillating Vocal Folds in a Biomimetic Larynx Model
No full textSynthetic silicone larynx models are essential for understanding the biomechanics of physiological and pathological vocal fold vibrations. The aim of this study is to investigate the effects of artificial ligament fibers on vocal fold vibrations in a synthetic larynx model, which is capable of replicating physiological laryngeal functions such as elongation, abduction, and adduction. A multi-layer silicone model with different mechanical properties for the musculus vocalis and the lamina propria consisting of ligament and mucosa was used. Ligament fibers of various diameters and break resistances were cast into the vocal folds and tested at different tension levels. An electromechanical setup was developed to mimic laryngeal physiology. The measurements included high-speed video recordings of vocal fold vibrations, subglottal pressure and acoustic. For the evaluation of the vibration characteristics, all measured values were evaluated and compared with parameters from ex and in vivo studies. The fundamental frequency of the synthetic larynx model was found to be approximately 200–520 Hz depending on integrated fiber types and tension levels. This range of the fundamental frequency corresponds to the reproduction of a female normal and singing voice range. The investigated voice parameters from vocal fold vibration, acoustics, and subglottal pressure were within normal value ranges from ex and in vivo studies. The integration of ligament fibers leads to an increase in the fundamental frequency with increasing airflow, while the tensioning of the ligament fibers remains constant. In addition, a tension increase in the fibers also generates a rise in the fundamental frequency delivering the physiological expectation of the dynamic behavior of vocal folds.</p
Dysderocrates tanatmisi sp. n., a new spider species from Turkey (Araneae, Dysderidae)
No full textWOS: 000418289800013A new species, Dysderocrates tanatmisi sp. n., is described on the basis of both sexes from the Mediterranean region of Turkey. Herein, we present the morphological and diagnostic characters and illustrations of the genitalia of both the male and female members of this species.Anatolian University Scientific Research Fund [1508F592]This study is a part of a master's thesis by the first author entitled "Dysderinae (Araneae, Dysderidae) Fauna in the Province of Antalya" and has been financed by Anatolian University Scientific Research Fund (Project no: 1508F592). We would like to thank Dr Miquel Arnedo (Barcelona, Spain), Dr Fulvio Gasparo (Trieste, Italy), and Kadir Bogac Kunt (Ankara, Turkey) for their comments on the new species, and Dr Ersen Aydin Yagmur (Manisa, Turkey) and Mert Elverici (Ankara, Turkey) for field work and contribution to the writing process of the manuscript
Acoustic analysis of professional singing masks
No full textWearing face coverings became one essential tool in order to prohibit virus transmission during the COVID-19 pandemic. In comparison to speaking and breathing, singing emits a much higher amount of aerosol particles. Therefore, there are situations in which singers can perform or rehearse only if they are using protective masks. However, such masks have a more or less adverse effect not only on the singer’s comfort and tightness of the mask but also on the radiated sound. For this reason, the spectral filtering and directivity of masks designed specifically for professional singing was measured. The tests were performed with a head phantom. Over most of the spectrum, attenuation is observed, although amplification happens at some low frequency bands for different mask types and directions. Especially singing masks with a plastic face shield showed partial amplification of up to +10 dB below a frequency of 2 kHz, while only slight significant attenuation and no amplification (minimal acoustic loss) were seen for woven fabric masks. Above 2.5 kHz, the transparent masks showed the greatest sound attenuation up to −30 dB, while woven fabric masks produced an overall lower sound attenuation of up to −5 dB. In addition at low frequencies, the sound was amplified or attenuated equally in all directions for masks with a stiff plastic face shield. At higher frequencies, the attenuation is higher to the frontal than to the backward direction
Overview on state-of-the-art numerical modeling of the phonation process
No full textNumerical modeling of the human phonatory process has become more and more in focus during the last two decades. The increase in computational power and the use of high-performance computation (HPC) yielded more complex models being closer to the actual fluid-structure-acoustic interaction (FSAI) within the human phonatory process. However, several different simulation approaches with varying mathematical complexity and focus on certain parts of the phonatory process exist. Currently, models are suggested based on ordinary differential equations (reduced order models) but also on partial differential equations based on continuum mechanics as e.g. the Navier–Stokes equations for the flow discretized by Finite-Volume or Finite-Element-Methods. This review will illuminate current trends and recent progress within the area. In summary, the ultimate simulation model satisfying all physiological needs and scientific opinions still has to be developed
Measurements of the hydrodynamic pressure on a surfboard fin during surfing
No full textAbstract The popularity of surfing has increased during the last 20 years with the growing number of river waves and artificial wave pools. For these different surfing conditions, hydrodynamic characteristics of boards and fins and their optimization become interesting for industry and science to analyze the biomechanics and physiology during surfing. In this work, a measuring system was developed assembled of four small pressure sensors included in a 3D-printed fin within a 2-fin configuration. The measurements were controlled by an acquisition board mounted into a surfboard. The system was initially tested in a water tank and exhibited a high accuracy of measured pressure. Afterwards, a surfer surfed the instrumented surfboard on a river wave and performed three cycles of surfing from one side of the wave channel to the other. The results showed a pressure difference between both sides of the instrumented fin that produces periodical lift forces directed away from the surfboard. Thereby, the maximum lift force was produced during the surfer’s motion from one side of the channel side to the other. It is assumed to increase the stability of the surfer’s back foot in combination with the right fin producing a lift force in opposite direction
