Investigation of resonance strategies of high pitch singing sopranos using dynamic three-dimensional magnetic resonance imaging

Articulatory and acoustic differences between lyric and dramatic singing in Western classical music

Within the realm of voice classification, singers could be sub-categorized by the weight of their repertoire, the so-called "singer's Fach." However, the opposite pole terms "lyric" and "dramatic" singing are not yet well defined by their acoustic and articulatory characteristics. Nine professional singers of different singers' Fach were asked to sing a diatonic scale on the vowel /a/, first in what the singers considered as lyric and second in what they considered as dramatic. Image recording was performed using real time magnetic resonance imaging (MRI) with 25 frames/s, and the audio signal was recorded via an optical microphone system. Analysis was performed with regard to sound pressure level (SPL), vibrato amplitude, and frequency and resonance frequencies as well as articulatory settings of the vocal tract. The analysis revealed three primary differences between dramatic and lyric singing: Dramatic singing was associated with greater SPL and greater vibrato amplitude and frequency as well as lower resonance frequencies. The higher SPL is an indication of voice source changes, and the lower resonance frequencies are probably caused by the lower larynx position. However, all these strategies showed a considerable individual variability. The singers' Fach might contribute to perceptual differences even for the same singer with regard to the respective repertoire.

Nasalance, Nasal Airflow and Perceived Nasality in Carnatic Singers and Non-singers

This study aims to compare the nasalance and nasal airflow between professional singers trained in Carnatic classical singing and non-singers. We also aimed to correlate perceived nasality with objective measurements of nasalance and nasal airflow. A total of 40 female participants (20 to 50 years) were involved in this study. The first group comprised 15 female professional Carnatic singers with a minimum of 10 years of classical training. The second group consisted of 25 non-singer females. These participants were compared on nasalance, nasal airflow and perceived nasality across three sets of stimuli (vowels, oral non-words, and nasal non-words) and three pitch-conditions (low, mid, and high). Correlations were also made between objective measures of nasalance and nasal airflow and perceived nasality. Mixed ANOVA showed a significant (P < 0.05) interaction in nasalance between pitch conditions and groups. Group differences were also observed in the nasalance scores of vowels, oral non-words, nasal non-words. There was a significant difference (P < 0.05) in nasalance with ascending pitch in singers and non-singers. A comparison of aerodynamic analysis of vowels, oral non-words, and nasal non-words between singers and non-singers suggested that nasal airflow was higher in singers. Perceptual nasality was significantly lower (P < 0.05) in Carnatic singers than non-singers. Correlations between objective measures of nasalance and nasal airflow and perceived nasality were not observed. Despite an increased airflow, nasality was lower in trained Carnatic singers than non-singers. Current findings suggest that vocal training impacts nasalance, nasal airflow and perceived nasality.

Dynamic changes of vocal tract dimensions with sound pressure level during messa di vocea)

The messa di voce (MdV), which consists of a continuous crescendo and subsequent decrescendo on one pitch is one of the more difficult exercises of the technical repertoire of Western classical singing. With rising lung pressure, regulatory adjustments both on the level of the glottis and the vocal tract are required to keep the pitch stable. The dynamic changes of vocal tract dimensions with the bidirectional variation of sound pressure level (SPL) during MdV were analyzed by two-dimensional real-time magnetic resonance imaging (25 frames/s) and synchronous audio recordings in 12 professional singer subjects. Close associations in the respective articulatory kinetics were found between SPL and lip opening, jaw opening, pharynx width, uvula elevation, and vertical larynx position. However, changes in vocal tract dimensions during plateaus of SPL suggest that perceived loudness could have been varied beyond the dimension of SPL. Further multimodal investigation, including the analysis of sound spectra, is needed for a better understanding of the role of vocal tract resonances in the control of vocal loudness in human phonation.

Estimating Formant Frequencies of Vowels Sung by Sopranos Using Weighted Linear Prediction

This study introduces the weighted linear prediction adapted to high-pitched singing voices (WLP-HPSV) method for accurately estimating formant frequencies of vowels sung by lyric sopranos. The WLP-HPSV method employs a variant of the WLP analysis combined with the zero-frequency filtering (ZFF) technique to address specific challenges in formant estimation from singing signals. Evaluation of the WLP-HPSV method compared to the LPC method demonstrated its superior performance in accurately capturing the spectral characteristics of synthetic /u/ vowels and the /a/ and /u/ natural singing vowels. The QCP parameters used in the WLP-HPSV method varied with pitch, revealing insights into the interplay between the vocal tract and glottal characteristics during vowel production. The comparison between the LPC and WLP-HPSV methods highlighted the robustness of the WLP-HPSV method in accurately estimating formant frequencies across different pitches.

Voice efficiency for different voice qualities combining experimentally derived sound signals and numerical modeling of the vocal tract

Purpose: Concerning voice efficiency considerations of different singing styles, from western classical singing to contemporary commercial music, only limited data is available to date. This single-subject study attempts to quantify the acoustic sound intensity within the human glottis depending on different vocal tract configurations and vocal fold vibration. Methods: Combining Finite-Element-Models derived from 3D-MRI data, audio recordings, and electroglottography (EGG) we analyzed vocal tract transfer functions, particle velocity and acoustic pressure at the glottis, and EGG-related quantities to evaluate voice efficiency at the glottal level and resonance characteristics of different voice qualities according to Estill Voice Training^®. Results: Voice qualities Opera and Belting represent highly efficient strategies but apply different vowel strategies and should thus be capable of predominate orchestral sounds. Twang and Belting use similar vowels, but the twang vocal tract configuration enabled the occurrence of anti-resonances and was associated with reduced vocal fold contact but still partially comparable energy transfer from the glottis to the vocal tract. Speech was associated with highly efficient glottal to vocal tract energy transfer, but with the absence of psychoactive strategies makes it more susceptible to noise interference. Falsetto and Sobbing apply less efficiently. Falsetto mainly due to its voice source characteristics, Sobbing due to energy loss in the vocal tract. Thus technical amplification might be appropriate here. Conclusion: Differences exist between voice qualities regarding the sound intensity, caused by different vocal tract morphologies and oscillation characteristics of the vocal folds. The combination of numerical analysis of geometries inside the human body and experimentally determined data outside sheds light on acoustical quantities at the glottal level.