Towards Improved Auditory-Perceptual Assessment of Timbres: Comparing Accuracy and Reliability of Four Deconstructed Timbre Assessment Models.

Timbre is a central quality of singing, yet remains a complex notion poorly understood in psychoacoustic studies. Previous studies note how no single acoustic variable or combinations of variables consistently predict timbre dimensions. Timbre varies on a continuum from darkest to lightest. These extremes are associated with laryngeal and vocal tract adjustments related to smaller and larger vocal tract area and variations in vocal fold vibratory characteristics. Perceptually, timbre assessment is influenced by spectral characteristics and formant frequency adjustments, though these dimensions are not independently perceived. Perceptual studies repeatedly demonstrate difficulties in correlating variations in timbre stimuli to specific measures. A recent study demonstrated how acoustic predictive salience of voice category and voice weight across pitches contribute to timbre assessments and concludes that timbre may be related to as-of-yet unknown factor(s). The purpose of this study was to test four different models for assessing timbre; one model focused on specific anatomy, one on listener intuition, one utilizing auditory anchors, and one using expert raters in a deconstructed timbre model with five specific dimensions. METHODS: Four independent panels were conducted with separate cohorts of professional singing teachers. Forty-one assessors took part in the anatomically focused panel, 54 in the intuition-based panel, 30 in the anchored panel, and 12 in the expert listener panel. Stimuli taken from live performances of well-known singers were used for all panels, representing all genders, genres, and styles across a large pitch range. All stimuli are available as Supplementary Materials. Fleiss' kappa values, descriptive statistics, and significance tests are reported for all panel assessments. RESULTS: Panels 1 through 4 varied in overall accuracy and agreement. The intuition-based model showed overall 45% average accuracy (SD ± 4%), k = 0.289 (<0.001) compared to overall 71% average accuracy (SD ± 3%), k = 0.368 (<0.001) of the anatomical focused panel. The auditory-anchored model showed overall 75% average accuracy (SD ± 8%), k = 0.54 (<0.001) compared with overall 83% average accuracy and agreement of k = 0.63 (<0.001) for panel 4. Results revealed that the highest accuracy and reliability were achieved in a deconstructed timbre model and that providing anchoring improved reliability but with no further increase in accuracy. CONCLUSION: Deconstructing timbre into specific parameters improved auditory perceptual accuracy and overall agreement. Assessing timbre along with other perceptual dimensions improves accuracy and reliability. Panel assessors' expert level of listening skills remain an important factor in obtaining reliable and accurate assessments of auditory stimuli for timbre dimensions. Anchoring improved reliability but with no further increase in accuracy. The study suggests that timbre assessment can be improved by approaching the percept through a prism of five specific dimensions each related to specific physiology and auditory-perceptual subcategories. Further tests are needed with framework-naïve listeners, nonmusically educated listeners, artificial intelligence comparisons, and synthetic stimuli to further test the reliability.

Towards Automated Vocal Mode Classification in Healthy Singing Voice-An XGBoost Decision Tree-Based Machine Learning Classifier.

Auditory-perceptual assessment is widely used in clinical and pedagogical practice for speech and singing voice, yet several studies have shown poor intra- and inter-rater reliability in both clinical and singing voice contexts. Recent advances in artificial intelligence and machine learning offer models for automated classification and have demonstrated discriminatory power in both pathological and healthy voice. This study develops and tests an XGBoost decision tree based machine learning classifier to develop automated vocal mode classification in healthy singing voice. Classification models trained on mel-frequency cepstrum coefficients, MFCC-Zero-Time Windowing, glottal features, voice quality features, and α-ratios demonstrated 92% average F1-score accuracy in distinguishing metallic and non-metallic singing for male singers and 87% average F1-score for female singers. The model distinguished vocal modes with 70% and 69% average F1-score for male and female samples, respectively. Model performance was compared to human auditory-perceptual assessments of 64 corresponding samples performed by 41 professional singers. The model performed with approximating or subpar performance to human assessors on task-matched problems. The XGBoost gains observed across tested features reveal that the most important attributes for the tested classification problems were MFCCs and α-ratios between high and low frequency energy, with models trained on only these features achieving performance not statistically significantly different from the best tested models. The best automated models in this study do not yet match human auditory-perceptual discrimination but improve on previously reported F1-average accuracies in automated classification in singing voice.

A mixed-method feasibility study of the use of the Complete Vocal Technique (CVT), a pedagogic method to improve the voice and vocal function in singers and actors, in the treatment of patients with muscle tension dysphonia: a study protocol.

BACKGROUND: Muscle tension dysphonia (MTD) results from inefficient or ineffective voice production and is the cause of voice and throat complaints in up to 40% of patients presenting with hoarseness. Standard treatment is voice therapy (SLT-VT) delivered by specialist speech therapists in voice disorders (SLT-V). The Complete Vocal Technique (CVT) is a structured, pedagogic method which helps healthy singers and other performers optimise their vocal function enabling them to produce any sound required. The aim of this feasibility study is to investigate whether CVT administered by a trained, non-clinical CVT practitioner (CVT-P) can be applied to patients with MTD before progressing to a pilot randomised control study of CVT voice therapy (CVT-VT) versus SLT-VT. METHODS/DESIGN: In this feasibility study, we use a mixed-method, single-arm, prospective cohort design. The primary aim is to demonstrate whether CVT-VT can improve the voice and vocal function in patients with MTD in a pilot study using multidimensional assessment methods. Secondary aims are to assess whether (1) a CVT-VT study is feasible to perform; (2) is acceptable to patients, the CVT-P and SLT-VTs; and (3) whether CVT-VT differs from existing SLT-VT techniques. A minimum of 10 consecutive patients with a clinical diagnosis of primary MTD (types I-III) will be recruited over a 6-month period. Up to 6 video sessions of CVT-VT will be delivered by a CVT-P using a video link. The primary outcome will be a change in pre-/post-therapy scores of a self-reported patient questionnaire (Voice Handicap Index (VHI)). Secondary outcomes include changes in throat symptoms (Vocal Tract Discomfort Scale), acoustic/electroglottographic and auditory-perceptual measures of voice. Acceptability of the CVT-VT will be assessed prospectively, concurrently and retrospectively both quantitatively and qualitatively. Differences from SLT-VT will be assessed by performing a deductive thematic analysis of CVT-P transcripts of therapy sessions. CONCLUSION: This feasibility study will provide important data to support whether to proceed with a randomised controlled pilot study focusing on the effectiveness of the intervention compared to standard SLT-VT. Progression criteria will be based on demonstrating a positive outcome in treatment, successful delivery of the pilot study protocol, acceptability to all stakeholders and satisfactory recruitment rates. TRIAL REGISTRATION: ClinicalTrials.gov website ( NCT05365126 Unique Protocol ID: 19ET004). Registered on 06 May 2022.

Extreme Vocals-A Retrospective Longitudinal study of Vocal Health in 20 Professional Singers Performing and Teaching Rough Vocal Effects.

BACKGROUND: Rough vocal effects, extreme, or extended vocal techniques to sound intentionally hoarse or rough are an integral part of many genres and styles, and research has recently demonstrated the involvement of supraglottic narrowing and vibrations to produce such sounds. The vocal health of singing with rough vocal effects is poorly documented, especially in a longitudinal manner, while much vocal pedagogy continuously treats the sounds as harming to or dangerous for the vocal mechanism. OBJECTIVE: To longitudinally investigate the vocal health of professional singers who perform the five rough-sounding vocal effects Distortion, Growl, Grunt, Rattle, and Creaking as part of their singing and teaching. METHODS: Twenty singers underwent nasoendoscopic examination, filled in SVHI questionnaires, and were assessed by GRBAS with a 14-year interval in a retrospective longitudinal study (from 2007 to 2021). Endoscopic materials were assessed by Reflux Finding Score and a hybrid version of the Stroboscopy Rating Scale. RESULTS: Singers presented at initiation of study with an average SVHI of 9.2 (±9), which decreased at time of follow up 14 years later to an average of 5.12 (±6). Laryngeal assessments (RFS and SRS) revealed low averages at initiation of study as well as at conclusion of the study with only small fluctuations in averages, with findings mainly relating to arytenoid asymmetry. CONCLUSION: The participating singers perform and teach rough vocal effects continually and present with healthy laryngeal mechanisms and within-normal SVHI and GRBAS scores. The findings suggest that controlled supraglottic narrowing and techniques to allow for supraglottic structures to engage in vibration as an additional noise source can be performed sustainable and in a healthy manner if performed with correct vocal technique.

Assessing and Quantifying Air Added to the Voice by Means of Laryngostroboscopic Imaging, EGG, and Acoustics in Vocally Trained Subjects.

OBJECTIVE: To assess and quantify singers' strategies for adding air to phonation to sound "breathy" in a healthy manner STUDY DESIGN: Case-control study with 20 professional singers. METHODS: Twenty singers were recorded performing sustained vowels in the Complete Vocal Technique Neutral vocal mode with and without audible air added to the voice by means of laryngostroboscopic imaging using a videonasoendoscopic camera system, electroglottography, long-term average spectrum, as well as acoustic signals and audio perception. Singers completed Voice Handicap Index and Reflux Symptom Index questionnaires prior to examination. RESULTS: Air added to the voice resulted in an expected glottal gap along the length of the vocal folds, with little to no further difference in the supraglottic area, as compared with the Neutral phonation. Air added resulted in lowered Qx, mean Sound Pressure Level, and Cepstral Peak Prominence, but higher Harmonics-to-Noise Ratio, Jitter, and Shimmer, with decreased energy at the fundamental frequency. Adding audible air to the phonation did not exhibit similar effects on acoustics for males and females. Also, for females, H1-H2 difference decreased with air added, while it increased for males. CONCLUSION: Singers produce an audible airy phonation similar yet significantly different to the breathy phonation reported for both healthy and pathological speakers.

Extreme Vocal Effects Distortion, Growl, Grunt, Rattle, and Creaking as Measured by Electroglottography and Acoustics in 32 Healthy Professional Singers.

Vocal effects - also called extreme or extended vocal techniques - with the intention to sound hoarse or rough are widely used as part of many genres and styles of singing, yet scarcely documented in research. Physiological studies detail the involvement of supraglottic structures for the production of vocal effects, yet the acoustic impact of such involvement has not been documented systematically across phonation types. PURPOSE: To report acoustic measurements and electroglottography-specific measurements for the five rough-sounding vocal effects Distortion, Growl, Grunt, Rattle, and Creaking across phonation types to demonstrate differences between notes with and without vocal effects added. METHODS: Thirty-two professional singers and singing teachers produced sustained vowels in each of the four vocal modes with alternations of adding and removing the vocal effects. The singers were recorded with a microphone at a constant distance as well as with EGG. RESULTS: The vocal effects Distortion, Growl, Grunt, Rattle, and Creaking impact the acoustic spectra in separate and systematic ways across genders and phonation types. Each vocal effect impacted the spectrum in specific and particular frequency regions between 0 and 3.5 KHz as well as in higher partials after 12 kHz with statistical significance. EGG-waveforms were un-impacted by most of the vocal effects produced using supraglottic sound sources, whereas Grunt and Creaking conditions did impact EGG-waveform signals, though not consistently between participants. EGG measures confirmed sustained and unchanged Qx and Fx for most conditions, with statically significant changes in noise measurements Harmonic-to-Noise Ratio, Normalised Noise Energy, Relative Average Perturbation, and Cepstral Peak Prominence, despite Sound Pressure Level differing significantly only for a few specific conditions. Singers scored an average of 5,95 on Voice Handicap Index questionnaires and were all reportedly healthy. CONCLUSIONS: Vocal effects added to phonation produce specific increases and specific decreases in particular frequency regions in a systematic way and can be produced in a healthy and sustainable manner, as measured by Voice Handicap Index. Vocal effects can be added to different phonation types with differing acoustic output and singers were able to sustain and control involvement of the supraglottic sound source(s) independently of phonation type.

Deconstructing Timbre into 5 Physiological Parameters: Vocal Mode, Amount of Metal, Degree of Density, Size of Larynx, and Sound Coloring.

Timbre has been related to adjustment at the source as well as adjustments in resonance, including laryngeal height and hypopharynx area and volume. However, it is often presented in vocal pedagogy as solely related to resonance. Very little data is available on the laryngeal adjustments at both source and resonance involved in achieving various timbres across a variety of phonation types. PURPOSE: To systematically assess the independent laryngeal adjustments at the source and independent laryngeal adjustments in the vocal tract necessary to obtain the lightest and darkest timbral extremes for four different phonation types. METHODS: Twenty-one professional singers produced a sustained vowel "EH" as in "stay" in each of the four phonation types ("UH" as in "hungry" for one type), varying the sound coloring to the lightest and darkest of their ability without altering pitch, vowel, or loudness. The singers were observed using laryngostroboscopy and electroglottography. A systematic assessment protocol covering 31 laryngeal gestures was developed based on previous research for objectively classifying changes in laryngeal setups. RESULTS: Darkening and lightening the sound color involved altering the size of the vocal tract space related to lowering/raising the larynx, widening/closing the piriform sinuses, increasing/decreasing the distance between stylopharyngeus and palatopharyngeus, increasing/decreasing anterior-posterior narrowing (and the resulting view of the vocal folds), medialising/retracting ventricular folds, and altering supraglottic funnel depth. The phonation types did not show equal ability to be colored. Female singers exhibited less coloring variation compared to the males. Classical singing exhibited both lightening and darkening colouring features. CONCLUSIONS: The singers were able to produce a variety of different timbral expressions within each of the investigated four phonation types by coloring the sustained note darker or lighter using laryngeal adjustments. Timbre is deconstructed as a perceptual artefact defined by (1) the choice of vocal mode, (2) the amount of metallic character, (3) the degree of density in the note, (4) the chosen sound color, and (5) the natural size of the larynx and vocal tract.

Laryngostroboscopic Exploration of Rough Vocal Effects in Singing and their Statistical Recognizability: An Anatomical and Physiological Description and Visual Recognizability Study of Distortion, Growl, Rattle, and Grunt using laryngostroboscopic Imaging and Panel Assessment.

OBJECTIVES: To study vocal effects in singing from the pedagogical method complete vocal technique as related to specific and discrete supraglottic structures and activities by means of laryngostroboscopic imaging and panel testing. STUDY DESIGN: This is a case-control study with a double-panel assessment. METHODS: Twenty singers were recorded performing four of the rough vocal effects from the method Complete Vocal Technique. Two studies were performed: (1) Laryngostroboscopic examination using a videonasoendoscopic camera system and the Laryngostrobe program; (2) two blind-panel assessments with (a) voice clinicians and (b) singing teachers to investigate the recognizability of the vocal effects in supraglottic structures. RESULTS: The four investigated vocal effects could be related to particular and discrete vibratory pattern of supraglottic structures; Distortion as vibrations of the ventricular folds, Growl as vibrations of the arytenoid cartilages against the epiglottis, Rattle as the vibration of the arytenoid cartilages against one another, and Grunt as the vibrations of the whole supraglottic structure from level 1-4 at low frequencies with a large amplitude in the vibration of the vocal folds, with particular movement of the aryepiglottic folds. The two panels recognized the vocal effects with 91%/96% accuracy for Distortion, 91%/74% accuracy for Rattle, 90%/66% accuracy for Grunt, and 83%/99% accuracy for Growl, with an overall accuracy of 91%/84%. CONCLUSION: Vocal effects can be performed, identified, and recognized as particular vibratory patterns of supraglottic structures with no visible pathology in subjects performing the effects.