Influence of nasal cavities on voice quality: Computer simulations and experiments.

Nasal cavities are known to introduce antiresonances (dips) in the sound spectrum reducing the acoustic power of the voice. In this study, a three-dimensional (3D) finite element (FE) model of the vocal tract (VT) of one female subject was created for vowels [a:] and [i:] without and with a detailed model of nasal cavities based on CT (Computer Tomography) images. The 3D FE models were then used for analyzing the resonances, antiresonances and the acoustic pressure response spectra of the VT. The computed results were compared with the measurements of a VT model for the vowel [a:], obtained from the FE model by 3D printing. The nasality affects mainly the lowest formant frequency and decreases its peak level. The results confirm the main effect of nasalization, i.e., that sound pressure level decreases in the frequency region of the formants F1-F2 and emphasizes the frequency region of the formants F3-F5 around the singer's formant cluster. Additionally, many internal local resonances in the nasal and paranasal cavities were found in the 3D FE model. Their effect on the acoustic output was found to be minimal, but accelerometer measurements on the walls of the 3D-printed model suggested they could contribute to structure vibrations.

Bambusuril as a One-Electron Donor for Photoinduced Electron Transfer to Methyl Viologen in Mixed Crystals.

Methyl viologen hexafluorophosphate (MV2+·2PF6-) and dodecamethylbambus[6]uril (BU6) form crystals in which the layers of viologen dications alternate with those of a 1:2 supramolecular complex of BU6 and PF6-. This arrangement allows for a one-electron reduction of MV2+ ions upon UV irradiation to form MV+• radical cations within the crystal structure with half-lives of several hours in air. The mechanism of this photoinduced electron transfer in the solid state and the origin of the long-lived charge-separated state were studied by steady-state and transient spectroscopies, cyclic voltammetry, and electron paramagnetic resonance spectroscopy. Our experiments are supported by quantum-chemical calculations showing that BU6 acts as a reductant. In addition, analogous photochemical behavior is also demonstrated on other MV2+/BU6 crystals containing either BF4- or Br- counterions.

Evaluation of clinical value of videokymography for diagnosis and treatment of voice disorders.

This study aimed at determining the clinical value of videokymography (VKG) as an additional tool for the assessment of voice disorders. 105 subjects with voice disorders were examined by an experienced laryngologist. A questionnaire was used to specify diagnosis, diagnostic confidence, and treatment recommendations before and after VKG. The first part of questionnaire was filled by the laryngologist for each patient after routine ear-nose-throat evaluation, including stroboscopy, the second part after the subsequent VKG examination. In 31% of subjects VKG confirmed the stroboscopic diagnosis, in 44% it made the diagnosis more accurate, in 20% there was adjustment of the treatment, and in 5% it was not found diagnostically useful. After VKG the diagnostic confidence increased in 68% of the subjects. VKG may help clinicians to take some important treatment decisions and may be recommended to be performed in patients, where clinicians are uncertain about diagnosis and treatment.

Metal-Cation Recognition in Water by a Tetrapyrazinoporphyrazine-Based Tweezer Receptor.

A series of zinc azaphthalocyanines with two azacrowns in a rigid tweezer arrangement were prepared and the fluorescence sensing properties were investigated. The size-driven recognition of alkali and alkaline earth metal cations was significantly enhanced by the close cooperation of the two azacrown units, in which both donor nitrogen atoms need to be involved in analyte binding to switch the sensor on. The mono- or biphasic character of the binding isotherms, together with the binding stoichiometry and magnitude of association constants (KA ), indicated specific complexation of particular analytes. Water solvation was shown to play an important role and resulted in a strong quenching of sensor fluorescence in the ON state. The lead compound was embedded into silica nanoparticles and advantageous sensing properties towards K(+) were demonstrated in water (λF =671 nm, apparent KA =82 m(-1) , increase of 17×), even in the presence of (supra)physiological concentrations of Na(+) and Ca(2+) .

The softest sound levels of the human voice in normal subjects.

Accurate measurement of the softest sound levels of phonation presents technical and methodological challenges. This study aimed at (1) reliably obtaining normative data on sustained softest sound levels for the vowel [a:] at comfortable pitch; (2) comparing the results for different frequency and time weighting methods; and (3) refining the Union of European Phoniatricians' recommendation on allowed background noise levels for scientific and equipment manufacturers' purposes. Eighty healthy untrained participants (40 females, 40 males) were investigated in quiet rooms using a head-mounted microphone and a sound level meter at 30 cm distance. The one-second-equivalent sound levels were more stable and more representative for evaluating the softest sustained phonations than the fast-time-weighted levels. At 30 cm, these levels were in the range of 48-61 dB(C)/41-53 dB(A) for females and 49 - 64 dB(C)/35-53 dB(A) for males (5% to 95% quantile range). These ranges may serve as reference data in evaluating vocal normality. In order to reach a signal-to-noise ratio of at least 10 dB for more than 95% of the normal population, the background noise should be below 25 dB(A) and 38 dB(C), respectively, for the softest phonation measurements at 30 cm distance. For the A-weighting, this is 15 dB lower than the previously recommended value.

Glottal opening and closing events investigated by electroglottography and super-high-speed video recordings.

Previous research has suggested that the peaks in the first derivative (dEGG) of the electroglottographic (EGG) signal are good approximate indicators of the events of glottal opening and closing. These findings were based on high-speed video (HSV) recordings with frame rates 10 times lower than the sampling frequencies of the corresponding EGG data. The present study attempts to corroborate these previous findings, utilizing super-HSV recordings. The HSV and EGG recordings (sampled at 27 and 44 kHz, respectively) of an excised canine larynx phonation were synchronized by an external TTL signal to within 0.037 ms. Data were analyzed by means of glottovibrograms, digital kymograms, the glottal area waveform and the vocal fold contact length (VFCL), a new parameter representing the time-varying degree of 'zippering' closure along the anterior-posterior (A-P) glottal axis. The temporal offsets between glottal events (depicted in the HSV recordings) and dEGG peaks in the opening and closing phase of glottal vibration ranged from 0.02 to 0.61 ms, amounting to 0.24-10.88% of the respective glottal cycle durations. All dEGG double peaks coincided with vibratory A-P phase differences. In two out of the three analyzed video sequences, peaks in the first derivative of the VFCL coincided with dEGG peaks, again co-occurring with A-P phase differences. The findings suggest that dEGG peaks do not always coincide with the events of glottal closure and initial opening. Vocal fold contacting and de-contacting do not occur at infinitesimally small instants of time, but extend over a certain interval, particularly under the influence of A-P phase differences.

Complex vibratory patterns in an elephant larynx.

Elephants' low-frequency vocalizations are produced by flow-induced self-sustaining oscillations of laryngeal tissue. To date, little is known in detail about the vibratory phenomena in the elephant larynx. Here, we provide a first descriptive report of the complex oscillatory features found in the excised larynx of a 25 year old female African elephant (Loxodonta africana), the largest animal sound generator ever studied experimentally. Sound production was documented with high-speed video, acoustic measurements, air flow and sound pressure level recordings. The anatomy of the larynx was studied with computed tomography (CT) and dissections. Elephant CT vocal anatomy data were further compared with the anatomy of an adult human male. We observed numerous unusual phenomena, not typically reported in human vocal fold vibrations. Phase delays along both the inferior-superior and anterior-posterior (A-P) dimension were commonly observed, as well as transverse travelling wave patterns along the A-P dimension, previously not documented in the literature. Acoustic energy was mainly created during the instant of glottal opening. The vestibular folds, when adducted, participated in tissue vibration, effectively increasing the generated sound pressure level by 12 dB. The complexity of the observed phenomena is partly attributed to the distinct laryngeal anatomy of the elephant larynx, which is not simply a large-scale version of its human counterpart. Travelling waves may be facilitated by low fundamental frequencies and increased vocal fold tension. A travelling wave model is proposed, to account for three types of phenomena: A-P travelling waves, 'conventional' standing wave patterns, and irregular vocal fold vibration.

Determining the Mouth-to-Microphone Distance in Rigid Laryngoscopy: A Simple Solution Based on the Newly Measured Values of the Depth of Endoscope Insertion into the Mouth.

Mouth-to-microphone (MTM) distance is important when measuring the sound of voice. However, determining the MTM distance for laryngoscope-mounted microphones during laryngoscopic examinations is cumbersome. We introduce a novel solution for such cases, using the depth of insertion of the laryngoscope into the mouth DI as a reference distance. We measured the average insertion depth, DI, in 60 adult women and 60 adult men for rigid laryngoscopes with 70° and 90° view. We found the DI for the 70°/90° laryngoscope to be 9.7 ± 0.9/9.4 ± 0.6 cm in men, 8.9 ± 0.9/8.7 ± 0.7 cm in women, and 9.3 ± 0.9/9.0 ± 0.7 cm in all adults. Using these values, we show that, for microphones fixed at 15-40 cm from the tip of the laryngoscope, the final MTM distances are between 5 and 35 cm from the lips, and the standard uncertainties of these distances are between 16% and 2.5%. Our solution allows laryngologists and laryngoscope manufacturers to set and estimate the MTM distance for any rigid laryngeal endoscope with a microphone attached with reasonable accuracy, avoiding the need to measure this distance in vivo in routine practice.

Integrative Insights into the Myoelastic-Aerodynamic Theory and Acoustics of Phonation. Scientific Tribute to Donald G. Miller.

In this tribute article to D.G. Miller, we review some historical and recent contributions to understanding the myoelastic-aerodynamic (MEAD) theory of phonation and the related acoustic phenomena in subglottal and vocal tract. At the time of the formulation of MEAD by van den Berg in late 1950s, it was assumed that vocal fold oscillations are self-sustained thanks to increased subglottal pressure pushing the glottis to open and decreased subglottal pressure allowing the glottis to close. In vivo measurements of subglottal pressures during phonation invalidated these assumptions, however, and showed that at low fundamental frequencies subglottal pressure rather tends to reach a maximum value at the beginning of glottal closure and then exhibits damped oscillations. These events can be interpreted as transient acoustic resonance phenomena in the subglottal tract that are triggered by glottal closure. They are analogous to the transient acoustic phenomena seen in the vocal tract. Rather than subglottal pressure oscillations, a more efficient mechanism of transfer of aerodynamic energy to the vocal fold vibrations has been identified in the vertical phase differences (mucosal waves) making the glottal shape more convergent during glottis opening than during glottis closing. Along with other discoveries, these findings form the basis of our current understanding of MEAD.

Dynamic System Coupling in Voice Production.

Voice is a major means of communication for humans, non-human mammals and many other vertebrates like birds and anurans. The physical and physiological principles of voice production are described by two theories: the MyoElastic-AeroDynamic (MEAD) theory and the Source-Filter Theory (SFT). While MEAD employs a multiphysics approach to understand the motor control and dynamics of self-sustained vibration of vocal folds or analogous tissues, SFT predominantly uses acoustics to understand spectral changes of the source via linear propagation through the vocal tract. Because the two theories focus on different aspects of voice production, they are often applied distinctly in specific areas of science and engineering. Here, we argue that the MEAD and the SFT are linked integral aspects of a holistic theory of voice production, describing a dynamically coupled system. The aim of this manuscript is to provide a comprehensive review of both the MEAD and the source-filter theory with its nonlinear extension, the latter of which suggests a number of conceptual similarities to sound production in brass instruments. We discuss the application of both theories to voice production of humans as well as of animals. An appraisal of voice production in the light of non-linear dynamics supports the notion that voice production can best be described with a systems view, considering coupled systems rather than isolated contributions of individual sub-systems.

Validation of the Czech Version of the Voice Handicap Index.

OBJECTIVE(S): The present study aims to evaluate the reliability and construct validity of the Czech version of the Voice Handicap Index (VHI-CZ) and determine the cut-off value to distinguish dysphonic patients from nondysphonic individuals. STUDY DESIGN: Prospective study, Parallel group design. METHODS: The study investigated 100 adult patients with dysphonia, divided into three groups based on the etiology of the voice problem (neurogenic, functional, and structural). Out of these, 25 patients were used for test-retest analysis, and 45 patients to determine the responsiveness to change. The control group consisted of 51 healthy subjects. All 151 individuals completed the VHI-CZ and were examined with the videolaryngostroboscopy. The internal consistency (Cronbach's alpha), the test-retest reliability (Intra-class Correlation Coefficient, ICC), and the construct validity were analyzed and the normative cut-off value was determined. RESULTS: The internal consistency of the VHI-CZ was excellent (Cronbach α = 0.984), and test-retest reliability was also excellent (ICC = 0.95, P < 0.001). The correlation between the self-assessed severity of the voice disorder and the VHI-CZ score was strong (Spearman's ρ = 0.877, P < 0.001). The VHI scores differences between dysphonic and nondysphonic patients were statistically significant (Mann-Whitney U test, P < 0.001). The differences among the three etiological subgroups (neurogenic, functional, and structural) were also statistically significant (Kruskal-Wallis test, P < 0.001). Moreover, the differences in the VHI-CZ total scores between pretreatment and posttreatment were statistically significant (Wilcoxon test, P < 0.001). The cut-off score of 13 points was found, by the analysis of the Receiver Operating Characteristic (ROC, Youden Index), to be most suitable for preselecting dysphonic individuals. CONCLUSION: The existing VHI-CZ showed excellent reliability and construct validity. The Czech VHI is a useful and valid monitoring tool for clinicians.

Domestic cat larynges can produce purring frequencies without neural input.

Most mammals produce vocal sounds according to the myoelastic-aerodynamic (MEAD) principle, through self-sustaining oscillation of laryngeal tissues.1,2 In contrast, cats have long been believed to produce their low-frequency purr vocalizations through a radically different mechanism involving active muscle contractions (AMC), where neurally driven electromyographic burst patterns (typically at 20-30 Hz) cause the intrinsic laryngeal muscles to actively modulate the respiratory airflow. Direct empirical evidence for this AMC mechanism is sparse.3 Here, the fundamental frequency (fo) ranges of eight domestic cats (Felis silvestris catus) were investigated in an excised larynx setup, to test the prediction of the AMC hypothesis that vibration should be impossible without neuromuscular activity, and thus unattainable in excised larynx setups, which are based on MEAD principles. Surprisingly, all eight excised larynges produced self-sustained oscillations at typical cat purring rates. Histological analysis of cat larynges revealed the presence of connective tissue masses, up to 4 mm in diameter, embedded in the vocal fold.4 This vocal fold specialization appears to allow the unusually low fo values observed in purring. While our data do not fully reject the AMC hypothesis for purring, they show that cat larynges can easily produce sounds in the purr regime with fundamental frequencies of 25 to 30 Hz without neural input or muscular contraction. This strongly suggests that the physical and physiological basis of cat purring involves the same MEAD-based mechanisms as other cat vocalizations (e.g., meows) and most other vertebrate vocalizations but is potentially augmented by AMC.

Vocal fold vibratory behavior changes following surgical treatment of polyps investigated with high-speed videoendoscopy and phonovibrography.

OBJECTIVES: The goal of this study was to objectively quantify the changes in vocal fold vibratory characteristics before and after surgery with high-speed videoendoscopy and the image analysis tool phonovibrography. METHODS: High-speed videoendoscopic data, audio recordings, and Voice Handicap Index scores were collected from 8 subjects with a diagnosis of unilateral vocal fold polyps, before operation and at 1 week and 1 to 3 months after operation. We then analyzed the objective phonovibrographic patterns and parameters describing the vocal fold vibratory behavior. RESULTS: On phonovibrography, the visual representations of the vocal fold vibratory characteristics, from both the individual and the group data, demonstrated very different patterns before surgery and both 1 week and 1 to 3 months after surgery. The individual phonovibrograms obtained from the left and right true vocal folds clearly demonstrated the lesion site and its effects on the vocal fold vibratory characteristics for each subject. The improvements in amplitude and symmetry (relative vibratory amplitude and vibration amplitude symmetry) of vocal fold vibration were quantified; the difference was greatest between data from before surgery and data from 1 week after surgery. CONCLUSIONS: The visual phonovibrographic patterns and quantitative data revealed marked changes in vocal fold vibratory patterns after operation and continued improvement at 1 to 3 months.

Laryngeal and Acoustic Analysis of Chest and Head Registers Extended Across a Three-Octave Range: A Case Study.

Voice registers are assumed to be related to different laryngeal adjustments, but objective evidence has been insufficient. While chest register is usually associated with the lower pitch range, and head register with the higher pitch range, here we investigated a professional singer who claimed an ability to produce both these registers at every pitch, throughout her entire singing range. The singer performed separated phonations alternating between the two registers (further called chest-like and head-like) at all pitches from C3 (131 Hz) to C6 (1047 Hz). We monitored the vocal fold vibrations using high-speed video endoscopy and electroglottography. The microphone sound was recorded and used for blind listening tests performed by the three authors (insiders) and by six "naive" participants (outsiders). The outsiders correctly identified the registers in 64% of the cases, and the insiders in 89% of the cases. Objective analysis revealed larger closed quotient and vertical phase differences for the chest-like register within the lower range below G4 (<392 Hz), and also a larger closed quotient at the membranous glottis within the higher range above Bb4 (>466 Hz), but not between Ab4-A4 (415-440 Hz). The normalized amplitude quotient was consistently lower in the chest-like register throughout the entire range. The results indicate that that the singer employed subtle laryngeal control mechanisms for the chest-like and head-like phonations on top of the traditionally recognized low-pitched chest and high-pitched head register phenomena. Across all pitches, the chest-like register was produced with more rapid glottal closure that was usually, but not necessarily, accompanied also by stronger adduction of membranous glottis. These register changes were not always easily perceivable by listeners, however.

Simulated Laryngeal High-Speed Videos for the Study of Normal and Dysphonic Vocal Fold Vibration.

PURPOSE: Laryngeal high-speed videoendoscopy (LHSV) has been recognized as a highly valuable modality for the scientific investigations of vocal fold (VF) vibrations. In contrast to stroboscopic imaging, LHSV enables visualizing aperiodic VF vibrations. However, the technique is less well established in the clinical care of disordered voices, partly because the properties of aperiodic vibration patterns are not yet described comprehensively. To address this, a computer model for simulation of VF vibration patterns observed in a variety of different phonation types is proposed. METHOD: A previously published kinematic model of mucosal wave phenomena is generalized to be capable of left-right asymmetry and to simulate endoscopic videos instead of only kymograms of VF vibrations at single sagittal positions. The most influential control parameters are the glottal halfwidths, the oscillation frequencies, the amplitudes, and the phase delays. RESULTS: The presented videos demonstrate zipper-like vibration, pressed voice, voice onset, constant and time-varying left-right and anterior-posterior phase differences, as well as left-right frequency differences of the VF vibration. Video frames, videokymograms, phonovibrograms, glottal area waveforms, and waveforms of VF contact area relating to electroglottograms are shown, as well as selected kinematic parameters. CONCLUSION: The presented videos demonstrate the ability to produce vibration patterns that are similar to those typically seen in endoscopic videos obtained from vocally healthy and dysphonic speakers. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.20151833.

Anion-free bambus[6]uril and its supramolecular properties.

Methods for the preparation of anion-free bambus[6]uril (BU6) are presented. They are based on the oxidation of iodide anion, which is bound inside the macrocycle, utilizing dark oxidation by hydrogen peroxide or photooxidation in the presence of titanium dioxide. Anion-free BU6 was found to be insoluble in any of the investigated solvents; however, it dissolves in methanol/chloroform (1:1) or acetonitrile/water (1:1) mixtures in the presence of the tetrabutylammonium salt of a suitable anion. The association constants with halide ions, BF(4)(-), NO(3)(-), and CN(-), were measured by (1)H NMR spectroscopy. The highest association constant (8.9×10(5) M(-1)) was found for the 1:1 complex of BU6 with I(-) in acetonitrile/water mixture. A number of crystal structures of BU6 complexes with various anions were obtained. The influence of the anion size on the macrocycle diameter is discussed together with an unusual arrangement of the macrocycles into separate layers.

Anion binding by bambus[6]uril probed in the gas phase and in solution.

Electrospray ionization mass spectrometry (ESI-MS) is used to probe the binding of small anions to the macrocycle of bambus[6]uril. For the halide ions, the experimental patterns suggest F(-) < Cl(-) < Br(-) < I(-), which is consistent with the order of anion binding found in the condensed phase. Parallel equilibrium studies in the condensed phase establish the association constants of halide anions and bambus[6]uril in mixed solvents. A detailed analysis of the mass spectrometric data is used to shed light on the correlations between the binding constants in the condensed phase and the ion abundances observed using ESI-MS. From the analysis it becomes apparent that ESI-MS can indeed represent the situation in solution to some extent, but the sampling in the gas-phase experiment is not 1:1 compared to that in solution.

Vocal tract changes caused by phonation into a tube: a case study using computer tomography and finite-element modeling.

Phonation into a glass tube is a voice training and therapy method that leads to beneficial effects in voice production. It has not been known, however, what changes occur in the vocal tract during and after the phonation into a tube. This pilot study examined the vocal tract shape in a female subject before, during, and after phonation into a tube using computer tomography (CT). Three-dimensional finite-element models (FEMs) of the vocal tract were derived from the CT images and used to study changes in vocal tract input impedance. When phonating on vowel [a:] the data showed tightened velopharyngeal closure and enlarged cross-sectional areas of the oropharyngeal and oral cavities during and after the tube-phonation. FEM calculations revealed an increased input inertance of the vocal tract and an increased acoustic energy radiated out of the vocal tract after the tube-phonation. The results indicate that the phonation into a tube causes changes in the vocal tract which remain also when the tube is removed. These effects may help improving voice production in patients and voice professionals.

Membranous and cartilaginous vocal fold adduction in singing.

While vocal fold adduction is an important parameter in speech, relatively little has been known on the adjustment of the vocal fold adduction in singing. This study investigates the possibility of separate adjustments of cartilaginous and membranous vocal fold adduction in singing. Six female and seven male subjects, singers and non-singers, were asked to imitate an instructor in producing four phonation types: "aBducted falsetto" (FaB), "aDducted falsetto" (FaD), "aBducted Chest" (CaB), and "aDducted Chest" (CaD). The phonations were evaluated using videostroboscopy, videokymography (VKG), electroglottography (EGG), and audio recordings. All the subjects showed less posterior (cartilaginous) vocal fold adduction in phonation types FaB and CaB than in FaD and CaD, and less membranous vocal fold adduction (smaller closed quotient) in FaB and FaD than in CaB and CaD. The findings indicate that the exercises enabled the singers to separately manipulate (a) cartilaginous adduction and (b) membranous medialization of the glottis though vocal fold bulging. Membranous adduction (monitored via videokymographic closed quotient) was influenced by both membranous medialization and cartilaginous adduction. Individual control over these types of vocal fold adjustments allows singers to create different vocal timbres.

Subglottal pressure oscillations in anechoic and resonant conditions and their influence on excised larynx phonations.

Excised larynges serve as natural models for studying behavior of the voice source. Acoustic resonances inside the air-supplying tubes below the larynx (i.e., subglottal space), however, interact with the vibratory behavior of the larynges and obscure their inherent vibration properties. Here, we explore a newly designed anechoic subglottal space which allows removing its acoustic resonances. We performed excised larynx experiments using both anechoic and resonant subglottal spaces in order to analyze and compare, for the very first time, the corresponding subglottal pressures, electroglottographic and radiated acoustic waveforms. In contrast to the resonant conditions, the anechoic subglottal pressure waveforms showed negligible oscillations during the vocal fold contact phase, as expected. When inverted, these waveforms closely matched the inverse filtered radiated sound waveforms. Subglottal resonances modified also the radiated sound pressures (Level 1 interactions). Furthermore, they changed the fundamental frequency (fo) of the vocal fold oscillations and offset phonation threshold pressures (Level 2 interactions), even for subglottal resonance frequencies 4-10 times higher than fo. The obtained data offer the basis for better understanding the inherent vibratory properties of the vocal folds, for studying the impact of structure-acoustic interactions on voice, and for validation of computational models of voice production.