Tracking voice change after thyroidectomy: application of spectral/cepstral analyses

This study evaluates the utility of perioperative spectral and cepstral acoustic analyses to monitor voice change after thyroidectomy. Perceptual and acoustic analyses were conducted on speech samples (sustained vowel /α/ and CAPE-V sentences) provided by 70 participants (36 women and 34 men) at four study time points: prior to thyroid surgery and 2 weeks, 3 months and 6 months after thyroidectomy. Repeated measures analyses of variance focused on the relative amplitude of the dominant harmonic in the voice signal (cepstral peak prominence, CPP), the ratio of low-to-high spectral energy, and their respective standard deviations (SD). Data were also examined for relationships between acoustic measures and perceptual ratings of overall severity of voice quality. Results showed that perceived overall severity and the acoustic measures of the CPP and its SD (CPPsd) computed from sentence productions were significantly reduced at 2-week post-thyroidectomy for 20 patients (29% of the sample) who had self-reported post-operative voice change. For this same group of patients, the CPP and CPPsd computed from sentence productions improved significantly from 2-weeks post-thyroidectomy to 6-months post-surgery. CPP and CPPsd also correlated well with perceived overall severity (r = -0.68 and -0.79, respectively). Measures of CPP from sustained vowel productions were not as effective as those from sentence productions in reflecting voice deterioration in the post-thyroidectomy patients at the 2-week post-surgery time period, were weaker correlates with perceived overall severity, and were not as effective in discriminating negative voice outcome (NegVO) from normal voice outcome (NormVO) patients as compared to the results from the sentence-level stimuli. Results indicate that spectral/cepstral analysis methods can be used with continuous speech samples to provide important objective data to document the effects of dysphonia in a post-thyroidectomy patient sample. When used in conjunction with patient's self-report and other general measures of vocal dysfunction, the acoustic measures employed in this study contribute to a complete profile of the patient's vocal condition.     

Quantifying dysphonia severity using a spectral/cepstral-based acoustic index: Comparisons with auditory-perceptual judgements from the CAPE-V

This study investigated the relationship between acoustic spectral/cepstral measures and listener severity ratings in normal and disordered voice samples. CAPE-V sentence samples and the vowel /ɑ/were elicited from eight normal speakers and 24 patients with varying degrees of dysphonia severity. Samples were analysed for measures of the cepstral peak prominence (CPP), the ratio of low-to-high spectral energy, and their respective standard deviations. Perceptual ratings of overall severity were also obtained for all samples. Results showed that all acoustic variables combined in a four-factor model which correlated with perceived severity with R = 0.81 (R² = 0.65). For the vowel /ɑ/, a five-factor model incorporating all acoustic variables and gender correlated with perceived severity with R = 0.96 (R² = 0.91). Results indicate that a strong relationship between perceptual and acoustic estimates of dysphonia severity can be achieved in both continuous speech and vowel contexts using a model incorporating spectral/cepstral measures.     

The effect of age and vocal task on cepstral/spectral measures of vocal function in adult males

This study investigated the effect of aging on cepstral/spectral acoustic measures calculated from clinical stimuli (vowels and sentences from the Consensus Auditory Perceptual Evaluation of Voice). Thirty younger adult males (20–49 years of age) and thirty older males (50–79 years of age) produced sustained vowels and read a connected speech stimulus which were applied to cepstral/spectral acoustic analyses to derive the multiparametric measure of Cepstral/Spectral Index of Dysphonia (CSID). Results indicated that older males exhibited significantly greater CSID measures than younger males in connected speech (p?=?0.001; d?=?0.98), but not the vowel. Linear regression revealed a moderate correlation between age and CSID in connected speech. These results further inform our understanding of how aging influences voice production in varied contexts and how commonly utilised clinical voice tasks subjected to cepstral/spectral acoustic analyses might differentially inform our knowledge of underlying vocal physiology.     

Toward the development of an objective index of dysphonia severity: a four-factor acoustic model

During assessment and management of individuals with voice disorders, clinicians routinely attempt to describe or quantify the severity of a patient's dysphonia. This investigation used acoustic measures derived from sustained vowel samples to predict dysphonia severity (as determined by auditory-perceptual ratings), for a diverse set of voice samples obtained from 134 adult females, with and without voice disorders. Stepwise multiple regression analysis on all voice samples, followed by randomized and repeated cross-validation (random selection of 75% of the original 134 voice sample corpus; 100 iterations) indicated that a four-variable model comprised of time and spectral-based acoustic measures was able to strongly predict perceived severity of dysphonia (mean R = .880; mean R(2) = .775). A cepstral-based measure (CPP/EXP ratio) was determined to be the most significant contributor to the prediction of dysphonia severity, though it is clear that the addition of other acoustic measures (pitch sigma; shimmer (dB); and the Discrete Fourier Transformation ratio, a measure of low versus high frequency spectral energy) add substantially to the accurate prediction of severity. The results are interpreted and discussed with respect to the key acoustic characteristics that contributed to the prediction of severity, the value of identifying a subset of time and spectral-based acoustic measures which appear sensitive to a perceptually diverse set of voices, and the possible use of acoustic models in guiding auditory-perceptual ratings.     

Estimating dysphonia severity in continuous speech: Application of a multi-parameter spectral/cepstral model

The purpose of the study was to identify a sub-set of spectral/cepstral-based analysis methods that would most effectively predict dysphonia severity (as estimated via auditory-perceptual analysis) in samples of continuous speech. Acoustic estimates of dysphonia severity were used as an objective treatment outcomes measure in a set of pre- vs post-treatment speech samples. Pre- and post-treatment continuous speech samples from 104 females with primary muscle tension dysphonia (MTD) were rated by listeners using a 100 point visual analogue scale (VAS) and analysed acoustically with spectral/cepstral-based measures. Stepwise linear regression produced a three-factor model consisting of the cepstral peak prominence (CPP); the mean ratio of low-to-high frequency spectral energy; and the standard deviation of the ratio of low-to-high frequency spectral energy that was strongly correlated with perceived dysphonia severity ratings (R = .85; R² = .73). Mean differences between predicted vs perceptual ratings for pre- and post-treatment speech samples were < 6 points on the 100 point VAS; mean absolute differences between predicted and perceived ratings were < 16 points on the 100 point VAS (equivalent to within one scale value on commonly used 7-point equal-appearing interval rating scales). A multi-parameter acoustic model consisting of spectral/cepstral-based measures shows considerable promise as an objective measure of dysphonia severity in continuous speech, even across the diverse voice types and severities observed in pre- and post-treatment MTD speech samples.     

Intensive treatment of dysarthria secondary to stroke

This study investigated the impact of a well-defined behavioral dysarthria treatment on acoustic and perceptual measures of speech in four adults with dysarthria secondary to stroke. A single-subject A-B-A experimental design was used to measure the effects of the Lee Silverman Voice Treatment (LSVT(?) LOUD) on the speech of individual participants. Dependent measures included vocal sound pressure level, phonatory stability, vowel space area, and listener ratings of speech, voice and intelligibility. Statistically significant improvements (p < 0.05) in vocal dB SPL and phonatory stability as well as larger vowel space area were present for all participants. Listener ratings suggested improved voice quality and more natural speech post-treatment. Speech intelligibility scores improved for one of four participants. These data suggest that people with dysarthria secondary to stroke can respond positively to intensive speech treatments such as LSVT. Further studies are needed to investigate speech treatments specific to stroke.     

Voice analysis in adductor spasmodic dysphonia: Objective diagnosis and response to botulinum toxin

IntroductionAdductor-type spasmodic dysphonia is a task-specific focal dystonia characterized by involuntary laryngeal muscle spasms. Due to the lack of quantitative instrumental tools, voice assessment in patients with adductor-type spasmodic dysphonia is mainly based on qualitative neurologic examination. We evaluated patients with cepstral analysis and specific machine-learning algorithms and compared the results with those collected in healthy subjects. In patients, we also used cepstral analysis and machine-learning algorithms to investigate the effect of botulinum neurotoxin type A.MethodsWe investigated 60 patients affected by adductor-type spasmodic dysphonia before botulinum neurotoxin type A therapy and 60 age and gender-matched healthy subjects. A subgroup of 35 patients was also evaluated after botulinum neurotoxin type A therapy. We recorded the sustained emission of a vowel and a sentence by means of a high-definition audio recorder. Voice samples underwent cepstral analysis as well as machine-learning algorithm classification techniques.ResultsCepstral analysis was able to differentiate between healthy subjects and patients, but receiver operating characteristic curve analysis demonstrated that machine-learning algorithms achieved better results than cepstral analysis in differentiating healthy subjects and patients affected by adductor-type spasmodic dysphonia. Similar results were obtained when differentiating patients before and after botulinum neurotoxin type A therapy. Cepstral analysis and machine-learning measures correlated with the severity of voice impairment in patients before and after botulinum neurotoxin type A therapy.ConclusionsCepstral analysis and machine-learning algorithms are new tools that offer meaningful support to clinicians in the diagnosis and treatment of adductor-type spasmodic dysphonia.     

The role of prosody in a case of foreign accent syndrome (FAS)

Foreign accent syndrome (FAS) is a rare disorder characterized by the emergence of a perceived foreign accent following brain damage. The symptomotology, functional bases, and neural substrates of this disorder are still being elucidated. In this case study, acoustic analyses were performed on the speech of a 46‐year old monolingual female who presented with FAS of unknown aetiology. The patient had a pseudo‐accent frequently described as ‘Swedish’ or ‘Eastern European’. Stop consonant VOT, consonant burst spectra and duration, vowel durations, formant frequencies, and trajectories were analysed, along with prosodic cues for lexical stress assignment and sentence‐level intonation. Results indicated VOT values were generally preserved, while there was a strong tendency to realize the English alveolar flap as a full stop, and to produce flaps that had greater‐than‐normal closure durations. The spectral properties of the patient's vowels resembled those of normal talkers (with the possible exceptions of decreased F1 values for /i/ and slight differences in formant dynamics for /u/, /o/, /i/, and /?/). However, vowel durations were relatively long, contributing to exaggerated tense/lax contrasts. Token‐to‐token variability in vowel production was slightly higher than normal for duration, but not for formant frequency values. Lexical stress assignment was inaccurate and highly variable (with similar problems noted for non‐speech materials), and sentence level intonation showed occasional deviations from typical American English patterns. For this patient, an underlying timing/rhythm difficulty appeared responsible for the range of segmental and suprasegmental changes leading to the impression of a foreign accent.     

Friedreich Ataxia: Dysarthria Profile and Clinical Data

Friedreich ataxia (FRDA) is the most frequent recessive ataxia in the Western world. Dysarthria is a cardinal feature of FRDA, often leading to severe impairments in daily functioning, but its exact characteristics are only poorly understood so far. We performed a comprehensive evaluation of dysarthria severity and the profile of speech motor deficits in 20 patients with a genetic diagnosis of FRDA based on a carefully selected battery of speaking tasks and two widely used paraspeech tasks, i.e., oral diadochokinesis and sustained vowel productions. Perceptual ratings of the speech samples identified respiration, voice quality, voice instability, articulation, and tempo as the most affected speech dimensions. Whereas vocal instability predicted ataxia severity, tempo turned out as a significant correlate of disease duration. Furthermore, articulation predicted the overall intelligibility score as determined by a systematic speech pathology assessment tool. In contrast, neurologists’ ratings of intelligibility—a component of the “Scale for the Assessment and Rating of Ataxia”—were found to be related to perceived speech tempo. Obviously, clinicians are more sensitive to slowness of speech than to any other feature of spoken language during dysarthria evaluation. Our results suggest that different components of speech production and trunk/limb motor functions are differentially susceptible to FRDA pathology. Furthermore, evidence emerged that paraspeech tasks do not allow for an adequate scaling of speech deficits in FRDA.     

Acoustic analyses of two recovered cases of foreign accent syndrome

Recently, a growing number of studies have been published involving phonetic and acoustic analyses on the rare motor-speech disorder known as Foreign Accent Syndrome (FAS). These studies have relied on pre- and post-trauma speech samples to investigate the acoustic and phonetic properties of individual cases of FAS speech. This study presents detailed acoustic analyses of the speech characteristics of two new cases of FAS using identical pre- and post-recovery speech samples, thus affording a new level of control in the study of Foreign Accent Syndrome. Participants include a 48-year-old female who began speaking with an “Eastern European” accent following a traumatic brain injury, and a 45-year-old male who presented with a “British” accent following a subcortical cerebral vascular accident (CVA). The acoustic analysis was based on 18 real words comprised of the stop consonants /p/, /t/, /k/; /b/, /d/, /g/ combined with the peripheral vowels /i/, /a/ and /u/ and ending in a voiceless stop. Computer-based acoustic measures included: (1) voice onset time (VOT), (2) vowel durations, (3) whole word durations, (4) first, second and third formant frequencies, and (5) fundamental frequency. Formant frequencies were measured at three points in the vowel duration: (a) 20%, (b) 50%, and (c) 80% to assess differences in vowel ‘onglides’ and ‘offglides’. The acoustic analysis allowed precise quantification of the major phonetic features associated with the foreign quality of participants' FAS speech. Results indicated post-recovery changes in both duration and frequency measures, including a tendency toward more normal VOT production of voiced stops, changes in average vowel durations, as well as evidence from formant frequency values of vowel backing for both participants. The implications of this study for future research and clinical applications are also considered.     

A longitudinal study of voice before and after phonosurgery for removal of a polyp

The aim of the present investigation was to evaluate the acoustic parameters, perceptual estimation, and self-estimation of voice before, 1 month after, and 6 years after surgical removal of a vocal fold polyp. Subjects were five male patients who came to the Phoniatric Clinic because of breathiness. For all patients, a polyp of one vocal fold was diagnosed. The operation was performed using cold instruments based on the principles of contemporary phonosurgery aiming maximally at preserving the phonatory bridge of the vocal fold. The subjects were recorded in a sound-proof booth three times: before surgery, 1 month post-, and 6 years post-operation. The patients read a short tale and they pronounced a sustained vowel /a/. The following variables were measured: clinical (the distance of the polyp from the anterior commissure, the width of the polyp base and the size of the polyp), and acoustic (F0, jitter, shimmer, harmonic-to-noise ratio, voice turbulence index, degree of voice breaks, and long-term average spectrum). Acoustic variables were measured using the program Praat, while the estimation of voice quality was completed using the GRBAS scale and self-estimation questionnaire of the voice quality, which were answered by the patients. The results showed significant improvement in the variables investigated and improved patients satisfaction with their vocal health after the surgery.     

A longitudinal study of voice before and after phonosurgery for removal of a polyp

The aim of the present investigation was to evaluate the acoustic parameters, perceptual estimation, and self‐estimation of voice before, 1 month after, and 6 years after surgical removal of a vocal fold polyp. Subjects were five male patients who came to the Phoniatric Clinic because of breathiness. For all patients, a polyp of one vocal fold was diagnosed. The operation was performed using cold instruments based on the principles of contemporary phonosurgery aiming maximally at preserving the phonatory bridge of the vocal fold. The subjects were recorded in a sound‐proof booth three times: before surgery, 1 month post‐, and 6 years post‐operation. The patients read a short tale and they pronounced a sustained vowel /a/. The following variables were measured: clinical (the distance of the polyp from the anterior commissure, the width of the polyp base and the size of the polyp), and acoustic (F0, jitter, shimmer, harmonic‐to‐noise ratio, voice turbulence index, degree of voice breaks, and long‐term average spectrum). Acoustic variables were measured using the program Praat, while the estimation of voice quality was completed using the GRBAS scale and self‐estimation questionnaire of the voice quality, which were answered by the patients. The results showed significant improvement in the variables investigated and improved patients satisfaction with their vocal health after the surgery.     

Intensive voice treatment (LSVT) for patients with Parkinson's disease: a 2 year follow up

OBJECTIVES: To assess long term (24 months) effects of the Lee Silverman voice treatment (LSVT), a method designed to improve vocal function in patients with Parkinson's disease. METHODS: Thirty three patients with idiopathic Parkinson's disease were stratified and randomly assigned to two treatment groups. One group received the LSVT, which emphasises high phonatory-respiratory effort. The other group received respiratory therapy (RET), which emphasises high respiratory effort alone. Patients in both treatment groups sustained vowel phonation, read a passage, and produced a monologue under identical conditions before, immediately after, and 24 months after speech treatment. Change in vocal function was measured by means of acoustic analyses of voice loudness (measured as sound pressure level, or SPL) and inflection in voice fundamental frequency (measured in terms of semitone standard deviation, or STSD). RESULTS: The LSVT was significantly more effective than the RET in improving (increasing) SPL and STSD immediately post-treatment and maintaining those improvements at 2 year follow up. CONCLUSIONS: The findings provide evidence for the efficacy of the LSVT as well as the long term maintenance of these effects in the treatment of voice and speech disorders in patients with idiopathic Parkinson's disease.     

Swallowing and voice effects of Lee Silverman Voice Treatment (LSVT®): a pilot study

OBJECTIVE: To define the effects of Lee Silverman Voice Treatment (LSVT on swallowing and voice in eight patients with idiopathic Parkinson's disease. METHODS: Each patient received a modified barium swallow (MBS) in addition to voice recording before and after 1 month of LSVT. Swallowing motility disorders were defined and temporal measures of the swallow were completed from the MBS. Voice evaluation included measures of vocal intensity, fundamental frequency, and the patient's perception of speech change. RESULTS: before LSVT, the most prevalent swallowing motility disorders were oral phase problems including reduced tongue control and strength. Reduced tongue base retraction resulting in residue in the vallecula was the most common disorder in the pharyngeal stage of the swallow. Oral transit time (OTT) and pharyngeal transit time (PTT) were prolonged. After LSVT, there was an overall 51% reduction in the number of swallowing motility disorders. Some temporal measures of swallowing were also significantly reduced as was the approximate amount of oral residue after 3 ml and 5 ml liquid swallows. Voice changes after LSVT included a significant increase in vocal intensity during sustained vowel phonation as well as during reading. CONCLUSIONS: LSVT seemingly improved neuromuscular control of the entire upper aerodigestive tract, improving oral tongue and tongue base function during the oral and pharyngeal phases of swallowing as well as improving vocal intensity.     

The effect of speaking context on spectral- and cepstral-based acoustic features of normal voice

The effect of speaking context on four cepstral- and spectral-based acoustic measures was investigated in 20 participants with normal voice. Speakers produced three different continuous speaking tasks that varied in duration and phonemic content. Cepstral and spectral measures that can be validly derived from continuous speech were computed across the three speaking contexts. Cepstral peak prominence (CPP), low/high spectral ratio, and the standard deviation (SD) of the low/high spectral ratio did not significantly differ across speaking contexts, and correlations for the first two measures were strong among the three speaking tasks. The SD of the CPP showed significant task differences, and relationships between the speaking contexts were generally moderate. These findings suggest that in speakers with normal voice, the differing phonemic content across several frequently used speaking stimuli minimally impacted group means for three clinically relevant cepstral- and spectral-based acoustic measures.     

Toward an acoustic typology of motor speech disorders

Acoustic methods have progressed to the point that an acoustic typology of the motor speech disorders can be constructed from a parameteric assessment of the speech subsystems (e.g., phonation, nasal resonance, vowel articulation, consonant articulation, intonation, and rhythm). The results of this analysis can be interpreted in respect to global functions in speech (e.g., voice quality, intelligibility, and prosody). This paper reviews studies showing that specific acoustic analyses have demonstrated or potential value toward the overall goal of constructing acoustic profiles of dysarthria and apraxia of speech. Several different acoustic measures are relevant to the study of the motor speech disorders, and these are increasingly supported by normative data and by guidelines for clinical application. Examples of these applications are discussed for a variety of specific neurologic diseases or perceptual types of disorder. Acoustic studies are useful in the study of motor speech disorders and recent progress points to a parametric analysis.     

Instrumental dimensioning of normal and pathological phonation using acoustic measurements

The present study deals with the dimensions of normal and pathological phonation. Separation of normal voices from pathological voices is tested under different aspects. Using a new parametrization of voice-quality properties in the acoustic signal, the vowel productions of 534 speakers (267 M, 267 F) without any reported voice pathology and the productions of 534 gender-matched pathological speakers were considered. In a first step, a gender-specific separation of the two groups is supported by a number of significantly different parameter means. In a second step, a clustering technique differentiates three subgroups within each group and gender on the basis of the acoustic parameters. Further, a statistical examination of the correct assignment in the database (DB-classification) as "normal" or "pathological" shows that the two groups overlap to some extent. The overlap of speaker assignment indicates a phonation continuum through the multidimensional space extending from normal to pathological voices. The validity of a categorical distinction of normal and pathological phonation in the sense of an individual or group-orientated labelling of voice quality as "normal" or "pathological", respectively, is discussed.     

Acoustic voice analysis in untreated patients with Parkinson's disease

To quantify several acoustic features of the voice in patients with Parkinson's disease (PD) not treated with dopaminergic drugs, 22 PD patients and 28 age and sex-matched controls were studied. The Computerized Speech Lab 4300 program (Kay Elemetrics) was used. Two seconds of a sustained /a/ and a sentence were captured with a microphone and laryngograph equipment. Measures included fundamental frequency (F(0)), frequency perturbation (jitter), intensity perturbation (shimmer), and harmonic/noise ratio (HIN) of the vowel /a/, and frequency and intensity variability of a sentence, phonational range, dynamic range at the natural frequency, maximum phonational time and s z ratio. All subjects underwent indirect laryngoscopy and/or laryngeal fibroscopy. When compared to controls, PD patients showed higher jitter and shimmer, lower H N ratio, and lower frequency variability of the sentence in the microphonic signal and reported a higher frequency of presence of low voice intensity, monopitch, harshness, voice arrests, and tremor.