Adverse Effects of Environmental Noise on Acoustic Voice Quality Measurements

An accurate analysis of voice quality is imperative when using acoustic measurements to diagnose vocal pathologies. It is known that noise has a significant effect on the reliability and validity of acoustic voice measurements, but the precise relationship has not been established. The purpose of this study was to investigate the influence of noise on the accuracy, reliability, and validity of acoustic voice quality measurements while balancing for gender, age, intersubject and intrasubject variability, microphones, computer hardware, analysis software, and type of noise. Level of noise was precisely controlled. The specific focus of interest was to determine the critical levels of noise that can invalidate voice quality measurements and to generate practical recommendations. Results suggest that the recommended, acceptable, and unacceptable levels of noise in the acoustic environment are above 42 dB, above 30 dB, and below 30 dB signal-to-noise ratio, respectively.     

Voice Changes During Work: Subjective Complaints and Objective Measurements for Female Primary and Secondary Schoolteachers

The purpose of this investigation was to study voice changes during a working day. The subjects consisted of 33 female primary and secondary schoolteachers who recorded their first and last lessons during one school day. The subjects were studied both as one group and two subgroups (those with many and those with few voice complaints). Estimates of fundamental frequency (F0), sound pressure level (SPL), the standard deviations of these values (F0 SD; SPL SD) and F0 time (vibration time of vocal folds) were made. The most obvious change due to loading was the rise of F0 that was 9.7 Hz between the first and last lesson (P = 0.00). F0 increased more (12.8. Hz, P = 0.006) in the subgroup with few complaints.     

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).     

Objective Voice Analysis for Dysphonic Patients: A Multiparametric Protocol Including Acoustic and Aerodynamic Measurements

The purpose was to determine the clinical value of a multiparametric objective voice evaluation protocol including acoustic and aerodynamic parameters measured mainly on a sustained /a/. This was done by comparison with perceptual analysis of continuous speech by a jury composed of 6 experienced listeners. Voice samples (continuous speech) from 63 male patients with dysphonia and 21 control subjects with normal voices were recorded and assesed by a jury of listeners. The jury was instructed to classify voice samples according to the G (overall dysphonia) component of the GRBAS score on a 4-point scale ranging from 0 for normal to 3 for severe dysphonia. Objective parameters were recorded on an EVA^® workstation. As usual with this type of system, parameters were measured mainly on a sustained /a/. Measured parameters included fundamental frequency (F₀), intensity, jitter, shimmer, signal-to-noise ratio, Lyapunov coefficient (LC), oral airflow (OAF), maximum phonatory time (MPT), and vocal range (range). Estimated subglottic pressure (ESGP) was determined on a series of /pa/. Discriminant analysis was performed to detect correlation between jury classification and combinations of parameters. Results showed that a nonlinear combination of only six parameters (range, LC, ESGP, MPT, signal-to-noise ratio, and F₀) allowed 86% concordance with jury classification. Discussion deals with the relative importance of the different objective parameters for discriminant analysis. Special emphasis is placed on two measurements rarely made in routine clinical workup, i.e., estimated subglottic pressure and Lyapunov coefficient.     

Subjective and Objective Evaluation of Voice Quality in Patients With Asthma

OBJECTIVES: To evaluate the voice quality in patients with mild-to-moderate asthma by subjective and objective methods. STUDY DESIGN: Comparative, controlled, cross-sectional study. METHODS: Patients with mild-to-moderate asthma (n=40) and age- and sex-matched healthy controls (n=40) were included. Acoustic analyses were performed by the Multi-Dimensional Voice Program (MDVP; Kay Elemetrics Corporation, Lincoln Park, NJ) and the movements of the vocal cords were examined by videolaryngostroboscopy (VLS). In addition, the duration of illness, maximum phonation time, "s/z" values, and vital capacity were evaluated. Voice Handicap Index (VHI) and GRB scales were used for subjective evaluations. RESULTS: Maximum phonation time values were significantly shorter both in male and female asthma patients compared with controls (P<0.0001). Also, average shimmer values in MDVP were higher for both sexes in the patient group compared with controls (P=0.002 and P=0.04, respectively). There was a significant difference between female patients and sex-matched controls with regard to mean noise-to-harmonic ratio values (P=0.006). Female patients with asthma had higher average jitter values compared with sex-matched controls (P<0.0001). A significant difference was noted between asthma and control groups with regard to GRB scale (P<0.0001, P<0.001, and P<0.0001, respectively). The VHI score was above the normal limit in 16 (40%), and VLS findings were abnormal in 39 (97.5%) asthmatics. CONCLUSION: In asthmatic patients, maximum phonation time, frequency, and amplitude perturbation parameters were impaired, but the vital capacity and the duration of illness did not correlate with these findings.     

Objective Voice Quality Analysis Before and After Onset of Unilateral Vocal Fold Paralysis

This study was designed to investigate objective voice quality measurements in unilateral vocal fold paralysis (UVFP) by eliminating intersubject variability. To our knowledge this is the first report objectively analyzing paralytic dysphonia as compared to the same voice before onset of UVFP. The voices of two male subjects were prospectively recorded before and after the onset of iatrogenic UVFP (thoracic surgery).The following acoustic measurements of the vowel /a/ were performed using the CSL and MDVP (Kay Elemetrics): jitter, shimmer, harmonics-to-noise ratio, cepstral peak prominence, the relative energy levels of the first harmonic, the first formant and the third formant, the spectral slope in the low-frequency zone (0-1 kHz and 0-2 kHz), and the relative level of energy above 6 kHz. Distribution of spectral energy was analyzed from a long-term average spectrum of 40 seconds of text. Laryngeal aerodynamic measurements were obtained for one patient before and after onset of paralysis using the Aerophone II (Kay Elemetrics). Pitch and amplitude perturbation increased secondary to UVFP, while the harmonics-to-noise ratio and the cepstral peak prominence decreased. A relative increase in the mid-frequency and high-frequency ranges and a decrease in the low-frequency spectral slope were observed. Mean airflow rate and intraoral pressure increased, and glottal resistance and vocal efficiency decreased secondary to UVFP. The findings of this self-paired study confirm some but not all the results of previous studies. Measures involving the fundamental and the formants did not corroborate previous findings. Further investigation with vocal tract modeling is warranted.     

Protocol Challenges for On-the-Job Voice Dosimetry of Teachers in the United States and Finland

The occupational voice use of teachers has been an important research topic over the last 10 years. However, data collection on vocal loading in teachers at and away from the workplace poses significant challenges to the research protocol. The challenges include recruitment of subjects, voice data collection on the job, and subject compliance and retention. The present article offers recommendations for coping with these protocol difficulties. The recommendations are based on the authors' experiences with long-term, on-the-job voice dosimetry of large subject groups of teachers in the United States and Finland.