Effects of initial consonant, pneumotachographic mask, and oral pressure tube on vocal perturbation, harmonics-to-noise, and intensity measurements

Vocal perturbation, harmonics-to-noise, and intensity measures were obtained for 10 subjects during three experimental tasks: (a) prolonged /a/, (b) /pa/ with vowel prolonged, and (c) same as (b) with subjects wearing a pneumotachographic mask and oral pressure tube inserted between the lips. There were no statistically significant differences among the experimental conditions for any of the measures. The findings suggest that a single task may be used to obtain airflow, oral pressure, and acoustic measures of vocal performance. Observed differences in jitter and harmonic-to-noise means for the male and female speakers are discussed.     

Multimodal Standardization of Voice Among Four Multicultural Populations: Fundamental Frequency and Spectral Characteristics

A stratified random sample of 20 males and 20 females matched for physiological factors and cultural-linguistic markers were examined to determine differences in fundamental frequency and spectral characteristics during prolongation of three vowels: [a], [i], and [u]. The ethnic-gender breakdown included four sets of five male and five female subjects comprised of Caucasian and African-American speakers of standard American English, native Hindi Indian speakers, and native Mandarin Chinese speakers. Acoustic measures were analyzed using the Multidimensional Voice Program (Kay Elemetrics, Lincoln Park, NJ) (Model 4305) from which fundamental frequency and associated acoustic spectra were extracted from a 200-ms sample of each vowel token. Statistically significant group differences for the main effects of culture, race, and gender were found. The acoustic differences found are attributed to biomechanical, physiological, cultural, and linguistic factors.     

Perceptual and Acoustic Assessment of Voice Pathology and the Efficacy of Endolaryngeal Phonomicrosurgery

Values for acoustic voice measurements were obtained from 88 normal individuals and 98 pathological cases of mass lesions of vocal fold and 50 cases of unilateral vocal fold paralysis. Overall, all items reflecting perturbations of pitch and amplitude as well as glottal noise were significantly higher in the groups of patients compared with the normal group. The measurement of normalized noise energy (NNE) was found to be an optimum parameter for discrimination of normal/abnormal voices. The voices of patients with vocal fold nodules and vocal fold polyps were analyzed before endolaryngeal phonomicrosurgery (EPM) and 2 weeks after. Statistically significant (p < 0.01) improvement was achieved both in perceptual and acoustic analysis. EPM resulted in a significant decrease of mean jitter, shimmer, and NNE. Clinically, these measures provided documentable and measurable evidence of vocal function and were helpful for comparing patients with normal speakers. They also were useful for a thorough documentation of patient's voice pathology and for evaluation of the presurgical and postsurgical voice status.     

The Performance of the Time-Frequency Analysis Software (TF32) in the Acoustic Analysis of the Synthesized Pathological Voice

The purpose of this study was to examine the algorithm-measuring capabilities used in the Time-Frequency Analysis Software Program for 32-bit Windows (TF32) for measuring fundamental frequency (F0), its dependent measures, and signal-to-noise ratio (SNR). The stability, accuracy, and linearity of its algorithm to systematic changes in aspiration noise and/or spectral slope (to mimic the perceptual characteristics of breathiness, roughness, and hoarseness) were evaluated using its analysis output to five female and five male synthesized voices. TF32 was used to calculate F0, Jitter%, Shimmer%, and SNR for each of the synthesized signals. The findings indicate that although TF32 produced stable results for male synthesized samples, they were not accurate when measuring F0, Jitter%, and Shimmer% with the addition of noise and variations in open quotient independently and in combination. In contrast, TF32 was neither stable nor accurate in making the same measurements for female synthesized samples. However, TF32 was stable and accurate in measuring SNR for male and most of female voices. These results point to an inappropriate F0 extraction algorithm in TF32 and stress the need for further research to remediate the algorithm or to identify a superior one.     

Perceptual and Acoustic Characteristics of Voice Changes in Reflux Laryngitis Patients

The aim of the study was to outline the multidimensional perceptual, subjective, and instrumental acoustic voice changes in the group of reflux laryngitis (RL) patients. Data of multidimensional voice assessment of 108 RL patients and 90 healthy persons of the control group were subjected to comparative analysis. A slight hoarseness according to the GRB (G-grade, R- rough, B-breathy) scale was prevailing in the RL patients group. Statistically significant difference (P < 0.001) between RL patients group and the control group was found of all voice parameters measured, with the patients having worse results--increased mean jitter, shimmer, normalized noise energy, voice handicap index (VHI), and decreased parameters of phonetogram. The results of the study demonstrated that multidimensional voice assessment documented deteriorated voice quality and restricted phonation capabilities in the tested group of RL patients.     

Acoustic analysis of the singing and speaking voice in singing students

The singing power ratio (SPR) is an objective means of quantifying the singer's formant. SPR has been shown to differentiate trained singers from nonsingers and sung from spoken tones. This study was designed to evaluate SPR and acoustic parameters in singing students to determine if the singer-intraining has an identifiable difference between sung and spoken voices. Digital audio recordings were made of both sung and spoken vowel sounds in 55 singing students for acoustic analysis. SPR values were not significantly different between the sung and spoken samples. Shimmer and noise-to-harmonic ratio were significantly higher in spoken samples. SPR analysis may provide an objective tool for monitoring the student's progress.     

Judgments of voice quality and preference: Acoustic interpretations

Previous studies have shown that trained listeners are highly reliable in making perceptual judgments of several parameters of normal and pathologic voices. This study investigated objective measures of acoustic characteristics of high and low preference voices as determined by previous perceptual study. Four acoustic parameters were measured including harmonics-to-noise ratio, autocorrelation function, average jitter, and the standard deviation of the fundamental frequency. Useful correlations between perceptual and measured results were identified. Normal voices differ from pathologic voices in terms of the acoustic-perceptual relationships.     

Acoustic characteristics of children''s voice

Four acoustic measures were taken from voice recordings of 121 children between the ages of 64 and 134 months. Acoustic parameters were measured on a sustained neutral /a/ vowel, produced imitatively at normal pitch and loudness. Samples were analyzed for fundamental frequency, jitter, shimmer, and signal-to-noise ratio (SNR). Data are presented to characterize effects of age, sex, height, and weight on these acoustic parameters. Results indicate statistically significant relationships between frequency and sex, with higher frequencies for girls. Also significant is a positive relationship between shimmer and height and a negative relationship between SNR and height.     

Influence of Data Acquisition Environment on Accuracy of Acoustic Voice Quality Measurements

Accuracy of acoustic voice analysis is influenced by the quality of recording. Lately, articles have suggested that soundcards perform equivalently to specialized professional-grade data acquisition (DA) systems. The purpose of this study was to investigate the influence of DA environment (DA system and microphone) on acoustic voice quality measurement (VQM) while balancing for gender, age, intersubject and intrasubject variability, and analysis software. More specifically, the relative performance of different hardware environments and the relationship between their technical characteristics and VQM performance was investigated. The discretization error and the effective dynamic range of the different DA environments were measured. We used 3 software systems to record and measure separately 2000 acoustic samples of sustained phonation for fundamental frequency, jitter, and shimmer. Analyses of variance (ANOVA) were performed with these parameters as the dependent variables. The results of the study suggested that professional-grade DA hardware is strongly recommended to provide accurate and valid voice assessment. The fundamental frequency measurement differences across DA environments were highly correlated to the discretization error (r=1.00), whereas jitter and shimmer were highly correlated to the effective dynamic range of the DA environments (r=-0.68 and r=-0.86, respectively).     

Acoustic Measures and Self-reports of Vocal Fatigue by Female Teachers

This study investigated the relation of symptoms of vocal fatigue to acoustic variables reflecting type of voice production and the effects of vocal loading. Seventy-nine female primary school teachers volunteered as subjects. Before and after a working day, (1) a 1-minute text reading sample was recorded at habitual loudness and loudly (as in large classroom), (2) a prolonged phonation on [a:] was recorded at habitual speaking pitch and loudness, and (3) a questionnaire about voice quality, ease, or difficulty of phonation and tiredness of throat was completed. The samples were analyzed for average fundamental frequency (F0), sound pressure level (SPL), and phonation type reflecting alpha ratio (SPL [1-5 kHz]-SPL [50 Hz-1 kHz]). The vowel samples were additionally analyzed for perturbation (jitter and shimmer). After a working day, F0, SPL, and alpha ratio were higher, jitter and shimmer values were lower, and more tiredness of throat was reported. The average levels of the acoustic parameters did not correlate with the symptoms. Increase in jitter and mean F0 in loud reading correlated with tiredness of throat. The results seem to suggest that, at least among experienced vocal professionals, voice production type had little relevance from the point of view of vocal fatigue reported. Differences in the acoustic parameters after a vocally loading working day mainly seem to reflect increased muscle activity as a consequence of vocal loading.     

Acoustic Prediction of Voice Type in Women with Functional Dysphonia

The categorization of voice into quality type (ie, normal, breathy, hoarse, rough) is often a traditional part of the voice diagnostic. The goal of this study was to assess the contributions of various time and spectral-based acoustic measures to the categorization of voice type for a diverse sample of voices collected from both functionally dysphonic (breathy, hoarse, and rough) (n=83) and normal women (n=51). Before acoustic analyses, 12 judges rated all voice samples for voice quality type. Discriminant analysis, using the modal rating of voice type as the dependent variable, produced a 5-variable model (comprising time and spectral-based measures) that correctly classified voice type with 79.9% accuracy (74.6% classification accuracy on cross-validation). Voice type classification was achieved based on two significant discriminant functions, interpreted as reflecting measures related to "Phonatory Instability" and "F(0) Characteristics." A cepstrum-based measure (CPP/EXP ratio) consistently emerged as a significant factor in predicting voice type; however, variables such as shimmer (RMS dB) and a measure of low- vs. high-frequency spectral energy (the Discrete Fourier Transformation ratio) also added substantially to the accurate profiling and prediction of voice type. The results are interpreted and discussed with respect to the key acoustic characteristics that contributed to the identification of specific voice types, and the value of identifying a subset of time and spectral-based acoustic measures that appear sensitive to a perceptually diverse set of dysphonic voices.     

Comparisons of jitter, shimmer, and signal-to-noise ratio from directly digitized versus taped voice samples

The purpose of this study was to compare jitter, shimmer, and signal-to-noise ratio (SNR) measures obtained from tape-recorded samples with the same measures made on directly digitized voice samples, with use of the CSpeech acoustic analysis program. Subjects included 30 young women who phonated the vowel /a/ at a comfortable pitch and loudness level. Voice samples were simultaneously recorded and digitized, and the resulting perturbation measures for the two conditions were compared. Results indicated that there were small but statistically significant differences between percent jitter, percent shimmer, and SNR calculated from taped samples compared with the same measures calculated from directly digitized samples. It was concluded that direct digitization for clinical measures of vocal perturbation was most desirable, but that taped samples could be used, if necessary, with some caution.     

Relationship Between Masking Levels and Phonatory Stability in Normal-Speaking Women

Disruption of auditory feedback such as masking has been shown to influence vocal production. A reliable finding is an increase in intensity level; an increase in fundamental frequency (F0) is a less robust finding. Research is lacking concerning the effects of auditory masking on measures of phonatory stability such as jitter and harmonics-to-noise ratio (HNR). This study investigated changes in intensity, F0, jitter, and HNR in 22 normally speaking college aged women. Subjects produced the vowel /a/ under three conditions: no masking level (0-dB ML), 50-dB ML, and 80-dB ML. Significant differences between conditions emerged for intensity; means for the other measures were not significantly different. Intraindividual differences between conditions for each variable are discussed in the framework of auditory versus kinesthetic feedback.     

Acoustic analysis of induced vocal stressby means of cognitive workload tasks

The purpose of this study was to determine the acoustic effects on voice of three tasks of cognitive workload and their possible relationship to stress. Acoustic analysis was used to measure stress and workload in four experimental tasks and two experiments. In the first experiment, subjects performed cognitive workload tasks under a stressful condition, performing the tasks as rapidly as possible without errors and with the knowledge that any errors committed would reduce their grade in a course. The second condition was to perform the same tasks but without the condition of stress related to the final grade. Four testing conditions were included. One was a baseline measure in which subjects spelled the Spanish alphabet. The second was the reading of a tongue twister, the third was the reading of a tongue twister with delayed auditory feedback, and the fourth was spelling the Spanish alphabet in reverse order. In each condition the subjects prolonged the vowel /a/ for, approximately 5 sec. All subjects performed a test to determine their overall level of anxiety. The results suggest that in conditions of experimentally induced stress there is an increase in the fundamental frequency (F₀) relative to baseline, an increase in jitter and shimmer, an increase in the high-frequency harmonic energy, and a decrease in spectral noise.     

Harmonics-to-Noise Ratio: An Index of Vocal Aging

Distinguishing between vocal changes that occur with normal aging and those that are associated with disease is an important goal of research in voice. Several acoustic measures have been used in an attempt to illuminate the integrity of the vocal mechanism, including harmonics-to-noise ratio (HNR), jitter, and fundamental frequency (F₀). HNR is a measure that quantifies the amount of additive noise in the voice signal; jitter reflects the periodicity of vocal fold vibration. In this study, measures of HNR, jitter and F₀ were used to compare vocal function in three groups of normally speaking women: young adults, middle-aged adults, and elderly adults. Significant differences in HNR emerged between the elderly women and the other two groups. F₀ differences were also apparent between the elderly group and the two younger groups; there were no significant differences in jitter between the three groups. HNR was found to be a more sensitive index of vocal function than jitter. The significant lowering of HNR evident in the elderly speakers may be attributable in part to medications taken by the majority of these elderly subjects.