Acoustic measurement of overall voice quality in sustained vowels and continuous speech

Measurement of dysphonia severity involves auditory-perceptual evaluations and acoustic analyses of sound waves. Meta-analysis of proportional associations between these two methods showed that many popular perturbation metrics and noise-to-harmonics and others ratios do not yield reasonable results. However, this meta-analysis demonstrated that the validity of specific autocorrelation- and cepstrum-based measures was much more convincing, and appointed ‘smoothed cepstral peak prominence’ as the most promising metric of dysphonia severity. Original research confirmed this inferiority of perturbation measures and superiority of cepstral indices in dysphonia measurement of laryngeal-vocal and tracheoesophageal voice samples. However, to be truly representative for daily voice use patterns, measurement of overall voice quality is ideally founded on the analysis of sustained vowels ánd continuous speech. A customized method for including both sample types and calculating the multivariate Acoustic Voice Quality Index (i.e., AVQI), was constructed for this purpose. Original study of the AVQI revealed acceptable results in terms of initial concurrent validity, diagnostic precision, internal and external cross-validity and responsiveness to change. It thus was concluded that the AVQI can track changes in dysphonia severity across the voice therapy process. There are many freely and commercially available computer programs and systems for acoustic metrics of dysphonia severity. We investigated agreements and differences between two commonly available programs (i.e., Praat and Multi-Dimensional Voice Program) and systems. The results indicated that clinicians better not compare frequency perturbation data across systems and programs and amplitude perturbation data across systems. Finally, acoustic information can also be utilized as a biofeedback modality during voice exercises. Based on a systematic literature review, it was cautiously concluded that acoustic biofeedback can be a valuable tool in the treatment of phonatory disorders. When applied with caution, acoustic algorithms (particularly cepstrum-based measures and AVQI) have merited a special role in assessment and/or treatment of dysphonia severity

How Reliable Is the Auditory-Perceptual Evaluation of Phonation Onset Hardness?

BACKGROUND: Generally, phonation onset hardness has been similarly defined and categorized throughout literature. There are typically three categories: soft, breathy, and hard onset. Phonation onset hardness is relevant in both assessment and treatment of various voice disorders and is usually determined on an auditory-perceptual basis. However, as far as we know, reliability of clinical auditory-perceptual indications of phonation onset hardness has not been investigated yet. Therefore, this study aimed at evaluating intrarater as well as interrater reliability of auditory-perceptual assessment of phonation onset hardness by speech and language pathologists. METHODS: After deidentification, the sentence-initial word [e.rst] was extracted from read text recordings of 20 subjects with various voice disorders and complaints. These 20 samples were purposefully selected to represent as much as possible the whole phonation onset hardness continuum. The auditory-perceptual rating protocol consisted of the paired comparison paradigm, in which all listeners were asked to perceptually compare phonation onset hardness of every fragment with the other 19 samples. This resulted in a ranking of the 20 samples, from hardest to softest phonation onset. Four speech and language pathologists agreed to compare phonation onset hardness according to this paradigm. The single-measures intraclass correlation coefficient (ICC) for absolute agreement was applied to determine the degree of reliability within as well as between raters. RESULTS: Intrarater ICC's showed acceptable reliability for two raters, yet poor reliability for the other two raters. Interrater ICC's demonstrated low reliability in general. Zooming in on the ratings shows that three of four evaluators agreed on which sample had the softest phonation onset, and that only two raters agreed on which recording had the hardest phonation onset. DISCUSSION: It can be concluded that there is considerable variability within and across raters when asked to indicate the word with the hardest phonation onset. This is the first study to approach auditory interpretation of phonation onset hardness with the paired comparison task. Questions are raised about the clinical utility of phonation onset hardness perception, the potential role of training, and the importance of a more objective yet clinically feasible measurement tool