Evaluating the Effect of Voice Quality Covariance on Auditory-Perceptual Evaluation Using a Novel Two-Dimensional Magnitude Estimation Task.

PURPOSE: Most people with dysphonia present with voices that vary along more than one voice quality (VQ) dimension. This study sought to examine the effect of covariance between breathy and rough VQ in natural voices. METHOD: A two-dimensional matrix of 16 /a/ vowels was selected such that two VQ dimensions (breathiness and roughness) were sampled on a 4-point severity scale (none, mild, moderate, and severe). Ten listeners evaluated 480 stimuli (16 stimuli × 10 repetitions × 3 blocks) on one-dimensional magnitude estimation (1DME) tasks and a novel two-dimensional magnitude estimation (2DME) task that allowed for simultaneous measurement of breathiness and roughness. RESULTS: Data indicated high intra- and interrater reliabilities for both breathiness and roughness in the 2DME and 1DME tasks. Correlation analyses revealed a strong correlation between 2DME and 1DME judgments for breathiness and roughness (r > .95). There was also a minimal correlation between breathy and rough VQ in the 2DME task (r < .10). CONCLUSIONS: Covarying roughness or breathiness had less impact on the perception of the other VQ in natural dysphonic voices in 2DME compared to 1DME. An understanding and quantification of the perceptual interactions among the dimensions will aid in the refinement of computational models and in the establishment of the validity of clinical scales for VQ perception.

Effects of Vibratory Source on Auditory-Perceptual and Bio-Inspired Computational Measures of Pediatric Voice Quality.

OBJECTIVE: The vibratory source for voicing in children with dysphonia is classified into three categories including a glottal vibratory source (GVS) observed in those with vocal lesions or hyperfunction; supraglottal vibratory sources (SGVS) observed secondary to laryngeal airway injuries, malformations, or reconstruction surgeries; and a combination of both glottal and supraglottal vibratory sources called mixed vibratory source (MVS). This study evaluated the effects of vibratory source on three primary dimensions of voice quality (breathiness, roughness, and strain) in children with GVS, SGVS, and MVS using single-variable matching tasks and computational measures obtained from bio-inspired auditory models. METHODS: A total of 44 dysphonic voice samples from children aged 4-11 years were selected. Seven listeners rated breathiness, roughness, and strain of 1000-ms /ɑ/ samples using single-variable matching tasks. Computational estimates of pitch strength, amplitude modulation filterbank output, and sharpness were obtained through custom-designed MATLAB algorithms. RESULTS: Perceived roughness and strain were significantly higher in children with SGVS and MVS compared to children with GVS. Among the computational measures, only the modulation filterbank output resulted in significant differences among vibratory sources; a posthoc test revealed that children with SGVS had greater amplitude modulation than children with GVS, as expected from their rougher voice quality. CONCLUSIONS: The results indicate that the output of an auditory amplitude modulation filterbank model may capture characteristics of SGVS that are strongly related to the rough voice quality.

Development and Validation of a Single-Variable Comparison Stimulus for Matching Strained Voice Quality Using a Psychoacoustic Framework.

PURPOSE: Acoustic and perceptual quantification of vocal strain has been a vexing problem for years. To increase measurement rigor, a suitable single-variable matching stimulus for strain was developed and validated, based on the matching stimulus used previously for breathy and rough voice qualities. METHOD: A set of 21 comparison stimuli for a single-variable matching task (SVMT) was synthesized based on a speech-shaped sawtooth waveform mixed with speech-shaped noise. Variable bandpass filter gain in mid-to-high frequencies achieved a wide range of computed sharpness (in constant sharpness steps) and served as the independent variable for the SVMT. Ten natural /ɑ/ stimuli with a wide range of the primary voice quality of strain and a minimum of breathiness or roughness were selected and assessed using the SVMT. Natural voice samples and synthetic comparison stimuli were also assessed using a perceptual magnitude estimation (ME) task. RESULTS: ME data validated the correspondence of the set of comparison stimuli to varying perceived strain. Perceived strain magnitudes of the comparison stimuli increased significantly and linearly with computed sharpness (r 2 = .99). A linear regression revealed that strain matching values were significantly predicted by computed sharpness (r 2 = .96) and perceived strain magnitudes (r 2 = .95) of the natural voice stimuli. CONCLUSION: The perception of vocal strain is strongly associated with computed sharpness and is captured accurately and precisely using an SVMT, in which the independent variable is the bandpass filter gain (in steps of equal sharpness) applied to the comparison stimuli.

Interactions Between Breathy and Rough Voice Qualities and Their Contributions to Overall Dysphonia Severity.

PURPOSE: Dysphonic voices typically present multiple voice quality dimensions. This study investigated potential interactions between perceived breathiness and roughness and their contributions to overall dysphonia severity. METHOD: Synthetic stimuli based on four talkers were created to systematically map out potential interactions. For each talker, a stimulus matrix composed of 49 stimuli (seven breathiness steps × seven roughness steps) was created by varying aspiration noise and open quotient to manipulate breathiness and superimposing amplitude modulation of varying depths to simulate roughness. One-dimensional matching (1DMA) and magnitude estimation (1DME) tasks were used to measure perceived breathiness, roughness, their potential interactions, and overall dysphonia severity. Additional 1DME tasks were used to assess a set of natural stimuli that varied along both breathiness and roughness. RESULTS: For the synthetic stimuli, the 1DMA task indicated little interaction between the two voice qualities. For the 1DME task, breathiness magnitude was influenced by roughness step to a greater extent than roughness magnitude was influenced by breathiness step. The additive contributions of breathiness and roughness to overall severity gradually diminished with increasing breathiness and roughness steps, possibly reflecting a ceiling effect in the 1DME task. For the natural stimuli, little consistent interaction was observed between breathiness and roughness. CONCLUSIONS: The matching task revealed minimal interaction between perceived breathiness and roughness, whereas the magnitude estimation task revealed some interaction between the two qualities and their cumulative contributions to overall dysphonia severity. Task differences are discussed in terms of differences in response bias and the role of perceptual anchors. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.21313701.

Predicting Perceived Vocal Roughness Using a Bio-Inspired Computational Model of Auditory Temporal Envelope Processing.

PURPOSE: Vocal roughness is often present in many voice disorders but the assessment of roughness mainly depends on the subjective auditory-perceptual evaluation and lacks acoustic correlates. This study aimed to apply the concept of roughness in general sound quality perception to vocal roughness assessment and to characterize the relationship between vocal roughness and temporal envelop fluctuation measures obtained from an auditory model. METHOD: Ten /ɑ/ recordings with a wide range of roughness were selected from an existing database. Ten listeners rated the roughness of the recordings in a single-variable matching task. Temporal envelope fluctuations of the recordings were analyzed with an auditory processing model of amplitude modulation that utilizes a modulation filterbank of different modulation frequencies. Pitch strength and the smoothed cepstral peak prominence were also obtained for comparison. RESULTS: Individual simple regression models yielded envelope standard deviation from a modulation filter with a low center frequency (64.3 Hz) as a statistically significant predictor of vocal roughness with a strong coefficient of determination (r 2 = .80). Pitch strength and CPPS were not significant predictors of roughness. CONCLUSION: This result supports the possible utility of envelope fluctuation measures from an auditory model as objective correlates of vocal roughness.

Effects of Task Demands on Neural Correlates of Acoustic and Semantic Processing in Challenging Listening Conditions.

Purpose Listeners shift their listening strategies between lower level acoustic information and higher level semantic information to prioritize maximum speech intelligibility in challenging listening conditions. Although increasing task demands via acoustic degradation modulates lexical-semantic processing, the neural mechanisms underlying different listening strategies are unclear. The current study examined the extent to which encoding of lower level acoustic cues is modulated by task demand and associations with lexical-semantic processes. Method Electroencephalography was acquired while participants listened to sentences in the presence of four-talker babble that contained either higher or lower probability final words. Task difficulty was modulated by time available to process responses. Cortical tracking of speech-neural correlates of acoustic temporal envelope processing-were estimated using temporal response functions. Results Task difficulty did not affect cortical tracking of temporal envelope of speech under challenging listening conditions. Neural indices of lexical-semantic processing (N400 amplitudes) were larger with increased task difficulty. No correlations were observed between the cortical tracking of temporal envelope of speech and lexical-semantic processes, even after controlling for the effect of individualized signal-to-noise ratios. Conclusions Cortical tracking of the temporal envelope of speech and semantic processing are differentially influenced by task difficulty. While increased task demands modulated higher level semantic processing, cortical tracking of the temporal envelope of speech may be influenced by task difficulty primarily when the demand is manipulated in terms of acoustic properties of the stimulus, consistent with an emerging perspective in speech perception.

Developing Clinically Relevant Scales of Breathy and Rough Voice Quality.

The most common measurement tools used in the perceptual evaluation of voice quality yield ordinal data and thus do not support the establishment of mathematical relationships among different measurement values. This makes their interpretation challenging. Among the many desirable features of any psychophysical measurement tool is the ability to quantify the difference between two or more measurements and the ability to interpret the measurements in a manner that is related to the experience of the observer. The former allows one to compare among measurements using simple mathematics, while the latter allows that comparison to be interpreted in constructive ways. In this paper we describe the development of standard measurement scales for two dimensions of voice quality, following an approach that has been applied successfully to the perception of loudness. The scales follow step-by-step procedures used to develop the sone scale of loudness, which ties physical units to the perceptual estimates of loudness magnitude. Goals of the current work include development of analogous scales for the perception of breathy and rough voice qualities. First, the relationship between perceived voice quality and physical units were established using single-variable matching tasks. Second, the relationship between a change in physical units from the single-variable matching tasks and perceived voice quality magnitude were established using magnitude estimation tasks. Third, single reference points were identified on breathy and rough continuums. Finally, all points on the newly established voice quality continuums were rescaled relative to these arbitrary reference points. The proposed breathiness and roughness scales result in ratio-level data with standard measurement units that support quantitative comparisons of perceptual judgments. Such judgments can be used, for example, to compare magnitude of change pre- and post-treatment.

Using Pitch Height and Pitch Strength to Characterize Type 1, 2, and 3 Voice Signals.

OBJECTIVE: Classifying dysphonic voices as type 1, 2, and 3 signals based on their periodicity enables researchers to determine the validity of acoustic measures derived from them. Existing methods of signal typing are commonly performed by listening to the voice sample and visualizing them on narrow-band spectrograms that require training, time, and are subjective in nature. The current study investigated pitch-based metrics (pitch height and pitch strength) as correlates to characterizing voice signal types. The computational estimates were validated with perceptual judgments of pitch height and pitch strength. METHODS: Pitch height and pitch strength were estimated from Auditory-Sawtooth Waveform Inspired Pitch Estimator Prime algorithm for 30 dysphonic voice segments (10 per type). Ten listeners evaluated pitch height through a single-variable matching task and pitch strength through an anchored magnitude estimation task. One way analyses of variance were used to determine the effects of signal type on pitch height and pitch strength estimates. Relationship between computational and perceptual estimates was evaluated using correlation coefficients and their significance. RESULTS: There was a significant difference between signal types in both computational and perceptual pitch strength estimates. Periodic type 1 signals had greater pitch strength compared to type 2 and 3 signals. Auditory-Sawtooth Waveform Inspired Pitch Estimator Prime produced robust computational estimates of pitch height even in type 3 signals when compared to other acoustic software. Listeners were able to reliably judge pitch height in type 2 and 3 signals despite their lack of a clear fundamental frequency. CONCLUSIONS: Pitch height and pitch strength can be measured in all dysphonic voices irrespective of signal periodicity.

Reproducibility of Voice Parameters: The Effect of Room Acoustics and Microphones.

INTRODUCTION: Computer analysis of voice recordings is an integral part of the evaluation and management of voice disorders. In many practices, voice samples are taken in rooms that are not sound attenuated and/or sound-proofed; further, the technology used is rarely consistent. This will likely affect the recordings, and therefore, their analyses. OBJECTIVES: The objective of this study is to compare various acoustic outcome measures taken from samples recorded in a sound-proofed booth to those recorded in more common clinic environments. Further, the effects from six different commonly used microphones will be compared. METHODS: Thirty-six speakers were recorded while reading a text and producing sustained vowels in a controlled acoustic environment. The collected samples were reproduced by a Head and Torso Simulator and recorded in three clinical rooms and in a sound booth using six different microphones. Newer measures (eg, Pitch Strength, cepstral peak prominence, Acoustic Voice Quality Index), as well as more traditional measures (eg Jitter, Shimmer, harmonics-to-noise ratio and Spectrum Tilt), were calculated from the samples collected with each microphone and within each room. RESULTS: The measures which are more robust to room acoustic differences, background noise, and microphone quality include Jitter and smooth cepstral peak prominence, followed by Shimmer, Acoustic Voice Quality Index, harmonics-to-noise ratio, Pitch Strength, and Spectrum Tilt. CONCLUSIONS: The effect of room acoustics and background noise on voice parameters appears to be stronger than the type of microphone used for the recording. Consequently, an appropriate acoustical clinical space may be more important than the quality of the microphone.

Effects of Task Difficulty on Neural Processes Underlying Semantics: An Event-Related Potentials Study.

Purpose Improving the ability to listen efficiently in noisy environments is a critical goal for hearing rehabilitation. However, understanding of the impact of difficult listening conditions on language processing is limited. The current study evaluated the neural processes underlying semantics in challenging listening conditions. Method Thirty adults with normal hearing completed an auditory sentence processing task in 4-talker babble. Event-related brain potentials were elicited by the final word in high- or low-context sentences, where the final word was either highly expected or not expected, followed by a 4-alternative forced-choice response with either longer (1,000 ms), middle (700 ms), or shorter (400 ms) response time deadlines (RTDs). Results Behavioral accuracy was reduced, and reactions times were faster for shorter RTDs. N400 amplitudes, reflecting ease of lexical access, were larger when elicited by target words in low-context sentences followed by shorter compared with longer RTDs. Conclusions These results reveal that more neural resources are allocated for semantic processing/lexical access when listening difficulty increases. Differences between RTDs may reflect increased attentional allocation for shorter RTDs. These findings suggest that situational listening demands can impact the demands for cognitive resources engaged in language processing, which could significantly impact listener experiences across environments.

The Perception of Breathiness in the Voices of Pediatric Speakers.

BACKGROUND: The perception of pediatric voice quality has been investigated using clinical protocols developed for adult voices and acoustic analyses designed to identify important physical parameters associated with normal and dysphonic pediatric voices. Laboratory investigations of adult dysphonia have included sophisticated methods, including a psychoacoustic approach that involves a single-variable matching task (SVMT), characterized by high inter- and intra-listener reliability, and analyses that include bio-inspired models of auditory perception that have provided valuable information regarding adult voice quality. OBJECTIVES: To establish the utility of a psychoacoustic approach to the investigation of voice quality perception in the context of pediatric voices? METHODS: Six listeners judged the breathiness of 20 synthetic vowel stimuli using an SVMT. To support comparisons with previous data, stimuli were modeled after four pediatric speakers and synthesized using Klatt with five parameter settings that influence the perception of breathiness. The population average breathiness judgments were modeled with acoustic measures of loudness ratio, pitch strength, and cepstral peak. RESULTS: Listeners reliably judged the perceived breathiness of pediatric voices, as with previous investigations of breathiness in adult dysphonic voices. Breathiness judgments were accurately modeled by loudness ratio (r2 = 0.93), pitch strength (r2 = 0.91), and cepstral peak (r2 = 0.82). Model accuracy was not affected significantly by including stimulus fundamental frequency and was slightly higher for pediatric than for adult voices. CONCLUSIONS: The SVMT proved robust for pediatric voices spanning a wide range of breathiness. The data indicate that this is a promising approach for future investigation of pediatric voice quality.

Comparison of Pitch Strength With Perceptual and Other Acoustic Metric Outcome Measures Following Medialization Laryngoplasty.

INTRODUCTION: The diagnoses of voice disorders, as well as treatment outcomes, are often tracked using visual (eg, stroboscopic images), auditory (eg, perceptual ratings), objective (eg, from acoustic or aerodynamic signals), and patient report (eg, Voice Handicap Index and Voice-Related Quality of Life) measures. However, many of these measures are known to have low to moderate sensitivity and specificity for detecting changes in vocal characteristics, including vocal quality. OBJECTIVE: The objective of this study was to compare changes in estimated pitch strength (PS) with other conventionally used acoustic measures based on the cepstral peak prominence (smoothed cepstral peak prominence, cepstral spectral index of dysphonia, and acoustic voice quality index), and clinical judgments of voice quality (GRBAS [grade, roughness, breathiness, asthenia, strain] scale) following laryngeal framework surgery. METHODS: This study involved post hoc analysis of recordings from 22 patients pretreatment and post treatment (thyroplasty and behavioral therapy). Sustained vowels and connected speech were analyzed using objective measures (PS, smoothed cepstral peak prominence, cepstral spectral index of dysphonia, and acoustic voice quality index), and these results were compared with mean auditory-perceptual ratings by expert clinicians using the GRBAS scale. RESULTS: All four acoustic measures changed significantly in the direction that usually indicates improved voice quality following treatment (P < 0.005). Grade and breathiness correlated the strongest with the acoustic measures (|r| ~ 0.7) with strain being the least correlated. CONCLUSIONS: Acoustic analysis on running speech highly correlates with judged ratings. PS is a robust, easily obtained acoustic measure of voice quality that could be useful in the clinical environment to follow treatment of voice disorders.

Perceptual and Quantitative Assessment of Dysphonia Across Vowel Categories.

OBJECTIVES: This study aims to determine the sensitivity of perceptual and computational correlates of breathy and rough voice quality (VQ) across multiple vowel categories using single-variable matching tasks (SVMTs). METHODS: Sustained phonations of /a/, /i/, and /u/ from 20 dysphonic talkers (10 with primarily breathy voices and 10 with primarily rough voices) were selected from the University of Florida Dysphonic Voice Database. For primarily breathy voices, perceived breathiness was judged, and for primarily rough voices, perceived roughness was judged by the same group of 10 listeners using an SVMT with five replicates per condition. Measures of pitch strength, cepstral peak, and autocorrelation peak were applied to models of the perceptual data. RESULTS: Intra- and inter-rater reliability were high for both the breathiness and the roughness perceptual tasks. For breathiness judgments, the effect of vowel was small. Averaged over all talkers and listeners, breathiness judgments for /a/, /i/, and /u/ were -11.6, -11.2, and -12.2 dB noise-to-signal ratio, respectively. For roughness judgments, the effect of vowel was larger. The perceived roughness of /a/ was higher than /i/ or /u/ by 3 dB modulation depth. Pitch strength was the most accurate predictor of breathiness matching (r2 = 0.84-0.94 across vowels), and log-transformed autocorrelation peak was the most accurate predictor of roughness matching (r2 = 0.59-0.83 across vowels). CONCLUSIONS: Breathiness is more consistently represented across vowels for dysphonic voices than roughness. This work represents a critical step in advancing studies of voice quality perception from single vowels to running speech.

Objective Indices of Perceived Vocal Strain.

BACKGROUND: A limited number of experiments have investigated the perception of strain compared to the voice qualities of breathiness and roughness despite its widespread occurrence in patients who have hyperfunctional voice disorders, adductor spasmodic dysphonia, and vocal fold paralysis among others. OBJECTIVE: The purpose of this study is to determine the perceptual basis of strain through identification and exploration of acoustic and psychoacoustic measures. METHODS: Twelve listeners evaluated the degree of strain for 28 dysphonic phonation samples on a five-point rating scale task. Computational estimates based on cepstrum, sharpness, and spectral moments (linear and transformed with auditory processing front-end) were correlated to the perceptual ratings. RESULTS: Perceived strain was strongly correlated with cepstral peak prominence, sharpness, and a subset of the spectral metrics. Spectral energy distribution measures from the output of an auditory processing front-end (ie, excitation pattern and specific loudness pattern) accounted for 77-79% of the model variance for strained voices in combination with the cepstral measure. CONCLUSIONS: Modeling the perception of strain using an auditory front-end prior to acoustic analysis provides better characterization of the perceptual ratings of strain, similar to our prior work on breathiness and roughness. Results also provide evidence that the sharpness model of Fastl and Zwicker (2007) is one of the strong predictors of strain perception.

Pitch Strength as an Outcome Measure for Treatment of Dysphonia.

BACKGROUND: Measurement of treatment outcomes is critical for the spectrum of voice treatments (ie, surgical, behavioral, or pharmacological). Outcome measures typically include visual (eg, stroboscopic data), auditory (eg, Consensus Auditory-Perceptual Evaluation of Voice; Grade, Roughness, Breathiness, Asthenia, Strain), and objective correlates of vocal fold vibratory characteristics, such as acoustic signals (eg, harmonics-to-noise ratio, cepstral peak prominence) or patient self-reported questionnaires (eg, Voice Handicap Index, Voice-Related Quality of Life). Subjective measures often show high variability, whereas most acoustic measures of voice are only valid for signals where some degree of periodicity can be assumed. However, this assumption is often invalid for dysphonic voices where signal periodicity is suspect. Furthermore, many of these measures are not useful in isolation for diagnostic purposes. OBJECTIVE: We evaluated a recently developed algorithm (Auditory Sawtooth Waveform Inspired Pitch Estimator-Prime [Auditory-SWIPE']) for estimating pitch and pitch strength for dysphonic voices. Whereas fundamental frequency is a physical attribute of a signal, pitch is its psychophysical correlate. As such, the perception of pitch can extend to most signals irrespective of their periodicity. METHODS: Post hoc analyses were conducted for three groups of patients evaluated and treated for voice problems at a major voice center: (1) muscle tension dysphonia/functional dysphonia, (2) vocal fold mass(es), and (3) presbyphonia. All patients were recorded before and after surgical/behavioral treatment for voice disorders. Pitch and pitch strength for each speaker were computed with the Auditory-SWIPE' algorithm. RESULTS: Comparison of pre- and posttreatment data provides support for pitch strength as a measure of treatment outcomes for dysphonic voices.

Modeling of Breathy Voice Quality Using Pitch-strength Estimates.

BACKGROUND: The characteristic voice quality of a speaker conveys important linguistic, paralinguistic, and vocal health-related information. Pitch strength refers to the salience of pitch sensation in a sound and was recently reported to be strongly correlated with the magnitude of perceived breathiness based on a small number of voice stimuli. OBJECTIVE: The current study examined the relationship between perceptual judgments of breathiness and computational estimates of pitch strength based on the Aud-SWIPE (P-NP) algorithm for a large number of voice stimuli (330 synthetic and 57 natural). METHODS AND RESULTS: Similar to the earlier study, the current results confirm a strong relationship between estimated pitch strength and listener judgments of breathiness such that low pitch-strength values are associated with voices that have high perceived breathiness. Based on this result, a model was developed for the perception of breathy voice quality using a pitch-strength estimator. Regression functions derived between the pitch-strength estimates and perceptual judgments of breathiness obtained from matching task revealed a linear relationship for a subset of the natural stimuli. We then used this function to obtain predicted breathiness values for the synthetic and the remaining natural stimuli. CONCLUSIONS: Predicted breathiness values from our model were highly correlated with the perceptual data for both types of stimuli. Systematic differences between the breathiness of natural and synthetic stimuli are discussed.

Cepstral Peak Sensitivity: A Theoretic Analysis and Comparison of Several Implementations.

OBJECTIVE: The aim of this study was to develop a theoretic analysis of the cepstral peak (CP), to compare several CP software programs, and to propose methods for reducing variability in CP estimation. STUDY DESIGN: Descriptive, experimental study. METHODS: The theoretic CP value of a pulse train was derived and compared with estimates computed for pulse train WAV files using available CP software programs: (1) Hillenbrand's CP prominence (CPP) software (Western Michigan University, Kalamazoo, MI), (2) KayPENTAX (Montvale, NJ) Multi-Speech implementation of CPP, and (3) a MATLAB (The Mathworks, Natick, MA, version R2014a) implementation using cepstral interpolation. The CP variation was also investigated for synthetic breathy vowels. RESULTS: For pulse trains with period T samples, the theoretic CP is 1/2+ε/T, |ε|<0.1 for all pulse trains (ε=0 for integer T). For fundamental frequencies between 70 and 230Hz, the CP mean±standard deviation was 0.496±0.002 using cepstral interpolation and 0.29±0.03 using Hillenbrand's software, whereas CPP was 35.0±3.8dB using Hillenbrand's software and 20.5±2.7dB using KayPENTAX's software. The CP and CPP versus signal-to-noise ratio for synthetic breathy vowels were fit to a logistic model for the Hillenbrand (R(2)=0.92) and KayPENTAX (R(2)=0.82) estimators as well as an ideal estimator (R(2)=0.98), which used a period-synchronous analysis. CONCLUSIONS: The findings indicate that several variables unrelated to the signal itself impact CP values, with some factors introducing large variability in CP values that would otherwise be attributed to the signal (eg, voice quality). Variability may be reduced by using a period-synchronous analysis with Hann windows.

The psychophysics of roughness applied to dysphonic voice.

Roughness is a sound quality that has been related to the amplitude modulation characteristics of the acoustic stimulus. Roughness also is considered one of the primary elements of voice quality associated with natural variations across normal voices and is a salient feature of many dysphonic voices. It is known that the roughness of tonal stimuli is dependent on the frequency and depth of amplitude modulation and on the carrier frequency. Here, it is determined if similar dependencies exist for voiced speech stimuli. Knowledge of such dependencies can lead to a better understanding of the acoustic characteristics of vocal roughness along the continuum of normal to dysphonic and may facilitate computational estimates of vocal roughness. Synthetic vowel stimuli were modeled after talkers selected from the Satloff/Heman-Ackah disordered voice database. To parametrically control amplitude modulation frequency and depth, synthesized stimuli had minimal amplitude fluctuations, and amplitude modulation was superimposed with the desired frequency and depth. Perceptual roughness judgments depended on amplitude modulation frequency and depth in a manner that closely matched data from tonal carriers. The dependence of perceived roughness on amplitude modulation frequency and depth closely matched the roughness of sinusoidal carriers as reported by Fastl and Zwicker [(2007) Psychoacoustics: Facts and Models, 3rd ed. (Springer, New York)].

Psychometric properties associated with perceived vocal roughness using a matching task.

A psychophysical matching paradigm has been used to better quantify voice quality under laboratory conditions. The goals of this study were to establish which of two candidate comparison stimuli would best ensure that the range of perceived vocal roughness could be adequately bracketed using a matching task and to provide a general solution to the problem of estimating vocal roughness. Psychometric functions for roughness matching indicated that a speech-like sawtooth-plus-noise complex (20 dB signal-to-noise ratio) amplitude modulated by a sinusoidal function raised to the 4th power yielded a comparison stimulus with a perceptual dynamic range well suited for roughness matching.