Breathiness Ratings Research Articles

Formant-Aware Spectral Analysis of Sustained Vowels of Pathological Breathy Voice

This paper reports the effectiveness of formant-aware spectral parameters to predict the perceptual breathiness rating. A breathyvoice has a steeper spectral slope and higher turbulent noise than a normal voice. Measuring spectral parameters of acoustic signals over lower formant regions is a known approach to capture the properties related to breathiness. This study examines this approach by testing the contemporary spectral parameters and algorithms within the framework, alternate frequency band designs, and vowel effects. Sustained vowel recordings (/a/, /i/, and /u/) of speakers with voice disorders in the German Saarbrueken Voice Database were considered (n: 367). Recordings with signal irregularities, such as subharmonics or with roughness perception, were excluded from the study. Four speech language pathologists perceptually rated the recordings for breathiness on a 100-point scale, and their averages were used in the analysis. The acoustic spectra were segmented into four frequency bands according to the vowel formant structures. Five spectral parameters (intraband harmonics-to-noise ratio, HNR; interband harmonics ratio, HHR; interband noise ratio, NNR; and interband glottal-to-noise energy, GNE, ratio) were evaluated in each band to predict the perceptual breathiness rating. Four HNR algorithms were tested. Multiple linear regression models of spectral parameters, led by the HNRs, were shown to explain up to 85% of the variance in perceptual breathiness ratings. This performance exceeded that of the acoustic breathiness index (82%). Individually, the HNR over the first two formants best explained the variances in the breathiness (78%), exceeding the smoothed cepstrum peak prominence (74%). The performance of HNR was highly algorithm dependent (10% spread). Some vowel effects were observed in the perceptual rating (higher for /u/), predictability (5% lower for /u/), and model parameter selections. Strong per-vowel breathiness acoustic models were found by segmenting the spectrum to isolate the portion most affected by breathiness.

Auditory-perceptual Parameters as Predictors of Voice Acoustic Measures

Much research has examined the relationship between perceptual and acoustic measures. However, little is known about the prediction values of perceptual measures on an acoustic parameter. This study utilized simulated and disordered voice samples to investigate the prediction values of breathiness, roughness, and strain ratings on the selection of some time-based and spectral-based measures of voice quality. This study retrospectively analysed two sets of precollected data. The experimental data had been collected from nine trained speakers manipulating false vocal fold activity, true vocal fold mass, and larynx height. The voice-disordered data had been extracted from a clinical database for 68 patients with muscle tension voice disorders (MTVD). Both data sets had been perceptually rated for breathiness, roughness, and strain. Voice samples (prolonged vowel /ɑ/ and Rainbow Passage readings) had undergone acoustic analysis using Praat for harmonics-to-noise ratio (HNR) and the program "Analysis of Dysphonia in Speech and Voice" (ADSV) for cepstral peak prominence (CPP), Cepstral/Spectral Index of Dysphonia (CSID), and Low/High spectral ratio (L/H ratio). Perceptual parameters were regressed against these acoustic measures to test their prediction values. Reliability data showed satisfactory intra- and inter-reliability of perceptual ratings for both data sets. Breathiness significantly predicted CPP (both vocal tasks) and CSID (Rainbow Passage) in experimental data and predicted all the acoustic measures in MTVD data. Roughness significantly predicted HNR, CPP, and CSID in experimental data, and CPP (Rainbow Passage) and CSID (both vocal tasks) in MTVD data. Strain (both vocal tasks) significantly predicted L/H ratio in both data sets. Breathiness ratings predicted selection of HNR, CPP and CSID; roughness ratings predicted selection of CPP and CSID, and strain ratings predicted L/H ratio.

Voice Quality in Telephone Interviews: A preliminary Acoustic Investigation

To investigate the impact of standardized mobile phone recordings passed through a telecom channel on acoustic markers of voice quality and on its perception by voice experts in normophonic speakers. Continuous speech and a sustained vowel were recorded for fourteen female and ten male normophonic speakers. The recordings were done simultaneously with a head-mounted high-quality microphone and through the telephone network on a receiving smartphone. Twenty-two acoustic voice quality, breathiness and pitch-related measures were extracted from the recordings. Nine vocologists perceptually rated the G, R and B parameters of the GRBAS scale on each voice sample. The reproducibility, the recording type, the stimulus type and the gender effects, as well as the correlation between acoustic and perceptual measures were investigated. The sustained vowel samples are damped after one second. Only the frequencies between 100 and 3700Hz are passed through the telecom channel and the frequency response is characterized by peaks and troughs. The acoustic measures show a good reproducibility over the three repetitions. All measures significantly differ between the recording types, except for the local jitter, the harmonics-to-noise ratio by Dejonckere and Lebacq, the period standard deviation and all six pitch measures. The AVQI score is higher in telephone recordings, while the ABI score is lower. Significant differences between genders are also found for most of the measures; while the AVQI is similar in men and women, the ABI is higher in women in both recording types. For the perceptual assessment, the interrater agreement is rather low, while the reproducibility over the three repetitions is good. Few significant differences between recording types are observed, except for lower breathiness ratings on telephone recordings. G ratings are significantly more severe on the sustained vowel on both recording types, R ratings only on telephone recordings. While roughness is rated higher in men on telephone recordings by most experts, no gender effect is observed for breathiness on either recording types. Finally, neither the AVQI nor the ABI yield strong correlations with any of the perceptual parameters. Our results show that passing a voice signal through a telecom channel induces filter and noise effects that limit the use of common acoustic voice quality measures and indexes. The AVQI and ABI are both significantly impacted by the recording type. The most reliable acoustic measures seem to be pitch perturbation (local jitter and period standard deviation) as well as the harmonics-to-noise ratio from Dejonckere and Lebacq. Our results also underline that raters are not equally sensitive to the various factors, including the recording type, the stimulus type and the gender effects. Neither of the three perceptual parameters G, R and B seem to be reliably measurable on telephone recordings using the two investigated acoustic indexes. Future studies investigating the impact of voice quality in telephone conversations should thus focus on acoustic measures on continuous speech samples that are limited to the frequency response of the telecom channel and that are not too sensitive to environmental and additive noise.

Towards a Singing Voice Multi-Sensor Analysis Tool: System Design, and Assessment Based on Vocal Breathiness.

Singing voice is a human quality that requires the precise coordination of numerous kinetic functions and results in a perceptually variable auditory outcome. The use of multi-sensor systems can facilitate the study of correlations between the vocal mechanism kinetic functions and the voice output. This is directly relevant to vocal education, rehabilitation, and prevention of vocal health issues in educators; professionals; and students of singing, music, and acting. In this work, we present the initial design of a modular multi-sensor system for singing voice analysis, and describe its first assessment experiment on the ‘vocal breathiness’ qualitative characteristic. A system case study with two professional singers was conducted, utilizing signals from four sensors. Participants sung a protocol of vocal trials in various degrees of intended vocal breathiness. Their (i) vocal output, (ii) phonatory function, and (iii) respiratory behavior-per-condition were recorded through a condenser microphone (CM), an Electroglottograph (EGG), and thoracic and abdominal respiratory effort transducers (RET), respectively. Participants’ individual respiratory management strategies were studied through qualitative analysis of RET data. Microphone audio samples breathiness degree was rated perceptually, and correlation analysis was performed between sample ratings and parameters extracted from CM and EGG data. Smoothed Cepstral Peak Prominence (CPPS) and vocal folds’ Open Quotient (OQ), as computed with the Howard method (HOQ), demonstrated the higher correlation coefficients, when analyzed individually. DECOM method-computed OQ (DOQ) was also examined. Interestingly, the correlation coefficient of pitch difference between estimates from CM and EGG signals appeared to be (based on the Pearson correlation coefficient) statistically insignificant (a result that warrants investigation in larger populations). The study of multi-variate models revealed even higher correlation coefficients. Models studied were the Acoustic Breathiness Index (ABI) and the proposed multiple regression model CDH (CPPS, DOQ, and HOQ), which was attempted in order to combine analysis results from microphone and EGG signals. The model combination of ABI and the proposed CDH appeared to yield the highest correlation with perceptual breathiness ratings. Study results suggest potential for the use of a completed system version in vocal pedagogy and research, as the case study indicated system practicality, a number of pertinent correlations, and introduced topics with further research possibilities.

Evaluation of Phonatory Behavior and Voice Quality in Patients with Multiple Sclerosis Treated with Deep Brain Stimulation

The effect of deep brain stimulation (DBS) on phonatory behavior and voice quality in eight patients with multiple sclerosis (MS) was examined instrumentally and perceptually. The acoustic signals of vowel productions obtained from patients (produced with and without stimulation) and from a group of 16 healthy control speakers were analyzed to prove statistically the changes of phonatory behavior and voice quality. This is a randomized study. Firstly, a new parametrization was used to determine phonatory behavior. Secondly, a perceptual evaluation of voice quality of the same speech material was performed. With stimulation, phonation has a greater tendency to be strained. The results of perceptual evaluation support this strained phonation behavior under stimulation, resulting in a smaller degree of breathiness ratings of all raters. Without stimulation, an impaired and partly disturbed adduction of the vocal folds can be shown. These findings are also supported in the perceptual experiment providing a higher degree of hoarseness ratings of all raters for these signals. High-frequency electrical impulses to the thalamus in patients with MS influence the phonatory behavior of their vocal folds. The results suggest the need for long-term monitoring of phonatory behavior during DBS to initiate adequate treatments without delay.

Information conveyed by voices

Two approaches for dealing with interrater variability in voice quality judgments have recently been proposed. The first [Shrivastav et al., J. Speech Lang. Hear. Res. 48, 323–335 (2005)] advocates reducing rating errors after data collection by averaging many ratings of each voice by each rater and then standardizing the resulting means. The second [Gerratt and Kreiman, J. Acoust. Soc. Am. 110, 2560–2566 (2001)] controls rating error at the source by applying a method-of-adjustment task, which controls variability due to attention, variable internal standards, etc. Using this second method, we accounted for 87% of the variance in listeners perception of noise level for 40 voices. This low level of residual variance (errors) raises the following question: Does averaging ratings reduce the information within listeners responses along with measurement errors? To address this question, 20 listeners provided 10 breathiness ratings for 40 voices. The likelihood of exact listener agreement was calculated and compared to data from the method-of-adjustment task. We also compared amounts of variance accounted for by differences between voices in quality (a metric of information captured). We hypothesized that the averaging and standardizing approach would produce both lower interrater agreement and lower amounts of variance accounted for than the method of adjustment technique. [Work supported by the NIH/NIDCD.]

Objective acoustic and aerodynamic measures of breathiness in paralytic dysphonia.

This study was designed to determine which objective acoustic or aerodynamic parameters allowed a homogeneous group of patients with unilateral vocal fold paralysis (UVFP) to be distinguished from an age-matched and smoking-matched control group and to search for linear correlations between the objective parameters and the subjective breathiness ratings. Eight patients with recent-onset UVFP and 12 controls were prospectively studied. The acoustic parameters measured for the vowel /a/ at a comfortable frequency and intensity were: jitter, shimmer, harmonics-to-noise ratio, cepstral peak prominence, the difference between the levels of the first two harmonics and the relative energy above 6 kHz. Aerodynamic parameters included the mean flow rate during a sustained /a/ and intraoral pressure during the production of the phoneme /pi/. The long-term average spectrum was calculated for 40 s of text, and the relative average energies in four frequency bands were compared. Six judges rated a mid-/a/ sample using a five-parameter scale with four levels of severity. Nonparametric statistical analysis revealed significant differences ( P<.05) between the UVFP group and the control group for 14 of the 19 parameters studied. Correlations between the objective parameters and perceived breathiness differed in the two groups. Correlations were not always as expected as based on previous literature reports. These measurements provided an objective qualification of voice in patients with UVFP and successfully distinguished them from the normal controls. The objective acoustic and aerodynamic measurements had generally low linear correlations with breathiness ratings in the control group. Higher correlations were seen in the UVFP group, in which breathiness was best correlated with airflow measurements.

The Relationship Between Cepstral Peak Prominence and Selected Parameters of Dysphonia

Traditional measures of dysphonia vary in their reliability and in their correlations with perceptions of grade. Measurements of cepstral peak prominence (CPP) have been shown to correlate well with perceptions of breathiness. Because it is a measure of periodicity, CPP should also predict roughness. The ability of CPP and other acoustic measures to predict overall dysphonia and the subcategories of breathiness and roughness in pathological voice samples is explored. Preoperative and postoperative speech samples from 19 patients with unilateral recurrent laryngeal nerve paralysis who underwent operative intervention were analyzed by trained listeners and by measures of smoothed CPP (CPPS), noise-to-harmonic ratio (NHR), amplitude perturbation quotient (APQ), relative average perturbation (RAP), and smoothed pitch perturbation quotient (sPPQ). The data were analyzed with bivariate Pearson correlation statistics. Grade of dysphonia and breathiness ratings correlated better with measurements of CPPS than with the other measures. CPPS from samples of connected speech (CPPS-s) best predicted overall dysphonia. None of the measures were useful in predicting roughness.

Acoustic correlates of breathy vocal quality: dysphonic voices and continuous speech.

In an earlier study, we evaluated the effectiveness of several acoustic measures in predicting breathiness ratings for sustained vowels spoken by nonpathological talkers who were asked to produce nonbreathy, moderately breathy, and very breathy phonation (Hillenbrand, Cleveland, & Erickson, 1994). The purpose of the present study was to extend these results to speakers with laryngeal pathologies and to conduct tests using connected speech in addition to sustained vowels. Breathiness ratings were obtained from a sustained vowel and a 12-word sentence spoken by 20 pathological and 5 nonpathological talkers. Acoustic measures were made of (a) signal periodicity, (b) first harmonic amplitude, and (c) spectral tilt. For the sustained vowels, a frequency domain measure of periodicity provided the most accurate predictions of perceived breathiness, accounting for 92% of the variance in breathiness ratings. The relative amplitude of the first harmonic and two measures of spectral tilt correlated moderately with breathiness ratings. For the sentences, both signal periodicity and spectral tilt provided accurate predictions of breathiness ratings, accounting for 70%-85% of the variance.

Consistency and reliability of voice quality ratings for different types of speech fragments.

This study describes a perception experiment in which listeners were asked to rate voice fragments obtained from a variety of speakers on grade, breathiness, and roughness. Four different types of stimuli were presented to each listener. One type of stimulus was based on connected speech fragments; the other three were based on different segments of a sustained vowel, yielding a 200 msec vowel onset stimulus, a 200 msec post-onset stimulus, and a 1000 msec whole vowel stimulus. Analyses focused on the consistency and reliability of grade, roughness, and breathiness ratings. Results indicated that stimulus type had virtually no effect on either within- or between-listener consistency of the grade, breathiness, or roughness ratings. Rating reliability too was hardly influenced by stimulus type. When determined as a function of the overall degree of deviance of a voice, the reliability of breathiness and roughness ratings was slightly higher for whole vowel and vowel onset stimuli than for connected speech and post-onset stimuli. It is concluded that connected speech stimuli are not necessarily to be preferred over vowel-type stimuli for a perceptual evaluation of grade, roughness, or breathiness. The somewhat higher reliability of ratings on vowel onset and whole vowel stimuli as compared to the post-onset stimuli is taken as an indication that the onset part of a vowel may contain voice quality cues that are less salient in the most stable part of a vowel.

Acoustic correlates of breathy vocal quality.

The purpose of this study was to evaluate the effectiveness of several acoustic measures in predicting breathiness ratings. Recordings were made of eight normal men and seven normal women producing normally phonated, moderately breathy, and very breathy sustained vowels. Twenty listeners rated the degree of breathiness using a direct magnitude estimation procedure. Acoustic measures were made of: (a) signal periodicity, (b) first harmonic amplitude, and (c) spectral tilt. Periodicity measures provided the most accurate predictions of perceived breathiness, accounting for approximately 80% of the variance in breathiness ratings. The relative amplitude of the first harmonic correlated moderately with breathiness ratings, and two measures of spectral tilt correlated weakly with perceived breathiness.