Supraja Anand

Listener Perception of Monopitch, Naturalness, and Intelligibility for Speakers With Parkinson's Disease

PURPOSE Given the potential significance of speech naturalness to functional and social rehabilitation outcomes, the objective of this study was to examine the effect of listener perceptions of monopitch on speech naturalness and intelligibility in individuals with Parkinsons disease (PD). METHOD Two short utterances were extracted from monologue samples of 16 speakers with PD and 5 age-matched adults without PD. Sixteen listeners evaluated these stimuli for monopitch, speech naturalness and intelligibility using the visual sort and rate method. RESULTS Naïve listeners can reliably judge monopitch, speech naturalness, and intelligibility with minimal familiarization. While monopitch and speech intelligibility were only moderately correlated, monopitch and speech naturalness were highly correlated. CONCLUSIONS A great deal of attention is currently being paid to improvement of vocal loudness and thus speech intelligibility in PD. Our findings suggest that prosodic characteristics such as monopitch should be explored as adjuncts to this treatment of dysarthria in PD. Development of such prosodic treatments may enhance speech naturalness and thus improve quality of life.

Acoustic parameters critical for an appropriate vibrato.

BACKGROUND A plethora of investigations have studied the acoustic characteristics of vibrato such as the rate, extent, onset (time from initiation of phonation until the first peak of vibrato), and periodicity. Despite extensive research, the degree to which various parameters of vibrato contribute to its acceptability remain unclear. PURPOSE The present study sought to determine the psychoacoustical relationship of mean fundamental frequency (f(0)), modulation frequency (f(f0m)), modulation depth (d(f0m)), and intensity to the appropriateness or inappropriateness of vibrato. METHOD Phonation samples of eight voice majors singing at low, middle, and high pitches were obtained. A high fidelity vocoder (STRAIGHT; Kawahara, 1997) was used to resynthesize these vowels with systematic manipulations of f(f0m) and d(f0m) of the f(0) contours resulting in a total of 600 stimuli (8 singers×3 pitches×5 f(f0m) levels×5 d(f0m) levels). Nine listeners (four experts and five students) evaluated these stimuli for appropriateness of vibrato at two different presentation levels (70 and 90 dB sound pressure level). RESULTS Statistical analyses of the perceptual data suggest that appropriateness of vibrato tends to increase with mean f(0) and decrease with d(f0m.) Appropriateness of vibrato is greatest for f(f0m) value of 6 Hz, but decreases both above and below this frequency. CONCLUSION perceived appropriateness of vibrato results from an interaction of mean f(0), f(f0m), and d(f0m) of the vowel waveform.

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.

Prosodic changes in Parkinson's disease

Parkinson’s disease often results in a hypokinetic dysarthria, causing well-known effects on speech and voice. Speech from individuals with Parkinson’s is typically studied through listening tasks (i.e., by family members and naive listeners) and is known to affect intelligibility. However, the exact speech changes causing degradations in speech quality have not been defined. Previous investigations have focused on standard measures of mean fundamental frequency, intensity, and rate. We hypothesize that speech changes are present at the prosodic level in addition to at the acoustic level. To test this hypothesis, we collected spontaneous conversational speech samples from 15 individuals with Parkinson’s and 13 age-and-gender matched neurologically healthy speakers (Control group). Several parameters were extracted from the speech signal to describe rate, phrasing, and stress in addition to fundamental frequency and intensity. These measures were compared with listener ratings of intelligibility performed ...

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.

Comparing roughness in sustained phonations and connected speech using a matching task

Experiments on perception of dysphonic voice quality have typically relied on sustained vowel phonations. The strong preference for vowels could be explained by their ease of production, their time invariance, and by the absence of confounding articulatory (e.g., consonant, dialect) and prosodic (e.g., stress, rate) changes. However, the magnitude of roughness perceived from sustained vowels may not reflect the roughness in connected speech produced by the same speaker. We examined how stimulus type impacts the perception of roughness. Ten naive listeners judged roughness for both vowel /a/ and sentences selected from ten dysphonic speakers using a single-variable matching task. Stimuli were selected to ensure a continuum of vocal roughness for vowels. The intra- and inter-listener reliability estimated using intra-class correlation (ICC) as well as matching values and variability will be compared across each stimulus type. This work is essential for extending models of dysphonic voice quality perception ...

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.

Psychometric measurement of vocal strain using a matching task with sustained vowel stimuli

Psychometric measurement of voice quality is important for quantitative assessment of dysphonia. Previous work established the efficacy of a single-variable matching task to index vocal breathiness and roughness using appropriately designed comparison stimuli, providing a context-independent perceptual task that improves the validity and accuracy of perceptual data compared to magnitude estimation or rating tasks. Physiologically, vocal strain is characterized by excessive vocal fold adduction during phonation, resulting in a glottal pulse with a low duty cycle. The narrowing of the glottal pulse causes the excitation spectrum roll-off to decrease, resulting in a flattening of the spectrum and significant changes in spectral skewness and kurtosis [Moore et al., 1997]. Analogous to comparison stimuli for breathy and rough measurement, a set of noisy sawtooth waveforms was created using modified step filters that varied in spectral slope 1 dB/octave steps, producing a wide range of perceived strain in the c...

Measurement of vocal breathiness perception with a matching task for sustained phonation and running speech

Laboratory measurements of the perception of vocal breathiness typically employ recordings of sustained vowel phonations. Sustained vowels are thought to provide a good representation of the underlying vocal disorder and are relatively easy to produce, analyze, and synthesize. Clinical assessments of voice quality are sometimes based on the production of speech utterances that are more ecologically valid than sustained vowel phonation and that capture the dynamics of laryngeal function, breath support, and a variety of complex cognitive and neuromuscular challenges typically involved in natural speech. As a result, voice quality associated with running speech may correspond more closely with perceived handicap and may represent more relevant treatment targets than sustained vowels. In a listening experiment with naive listeners, breathy voice quality was evaluated for exemplars of sustained /a/ production as well as read speech from a selection of talkers that vary widely in terms of their vocal breathine...