Biomedical subjects

Dimitar D Deliyski

Publications and source records attributed to Dimitar D Deliyski.

7 recordsLinked to original sources

PubMed2006

Mucosal wave: a normophonic study across visualization techniques.

Visualization of vocal fold vibration is essential for accurate diagnoses and optimal treatment of persons with voice disorders. Recently, scientific and anecdotal reports have evidenced an increased amount of variation in the diagnostically relevant features of extent and symmetry of mucosal wave magnitude in normophonic speakers. The objectives of this study were to preliminarily ascertain the variation in mucosal wave magnitude and symmetry for normophonic speakers as assessed via standard and novel techniques, and compare findings across modal and pressed phonations. A correlational design with a multiple baseline across visualization methods approach was used. Mucosal wave presence, magnitude, and symmetry from 52 normophonic speakers were judged via stroboscopy, high-speed videoendoscopy (HSV) playback, mucosal wave playback, and mucosal wave kymography playback. Results demonstrate a prevalence of atypical magnitude and symmetry of mucosal wave during modal and pressed phonations by normophonic persons, differences across techniques, and a relationship between judgments and habitual fundamental frequency. Given the prevalence of mucosal wave magnitude and symmetry variations in the normophonic population, overdiagnosis may be possible without caution. The various visualization techniques provided unique information suggesting that it may be beneficial to use both full view and kymographic visualization techniques in combination. A major restriction of the current commercial HSV systems is the frame rate, typically limited to 2000 frames per second, which appears insufficient for most female habitual phonations.

Adolescent↗

PubMed2006

Acoustic voice analysis of prelingually deaf adults before and after cochlear implantation.

It is widely accepted that many severe to profoundly deaf adults have benefited from cochlear implants (CIs). However, limited research has been conducted to investigate changes in voice and speech of prelingually deaf adults who receive CIs, a population well known for presenting with a variety of voice and speech abnormalities. The purpose of this study was to use acoustic analysis to explore changes in voice and speech for three prelingually deaf males pre- and postimplantation over 6 months. The following measurements, some measured in varying contexts, were obtained: fundamental frequency (F0), jitter, shimmer, noise-to-harmonic ratio, voice turbulence index, soft phonation index, amplitude- and F0-variation, F0-range, speech rate, nasalance, and vowel production. Characteristics of vowel production were measured by determining the first formant (F1) and second formant (F2) of vowels in various contexts, magnitude of F2-variation, and rate of F2-variation. Perceptual measurements of pitch, pitch variability, loudness variability, speech rate, and intonation were obtained for comparison. Results are reported using descriptive statistics. The results showed patterns of change for some of the parameters while there was considerable variation across the subjects. All participants demonstrated a decrease in F0 in at least one context and demonstrated a change in nasalance toward the norm as compared to their normal hearing control. The two participants who were oral-language communicators were judged to produce vowels with an average of 97.2% accuracy and the sign-language user demonstrated low percent accuracy for vowel production.

Adult↗

PubMed2006

Regression tree approach to studying factors influencing acoustic voice analysis.

Multiple factors influence voice quality measurements (VQM) obtained during an acoustic voice assessment including: gender, intrasubject variability, microphone, environmental noise (type and level), data acquisition (DA) system, and analysis software. This study used regression trees to investigate the order and relative importance of these factors on VQM including interaction effects of the factors and how the outcome differs when the acoustic environment is controlled for noise. Twenty normophonic participants provided 20 voice samples each, which were recorded synchronously on five DA systems combined with six different microphones. The samples were mixed with five noise types at eight signal-to-noise ratio (SNR) levels. The resulting 80,000 audio samples were analyzed for fundamental frequency (F(0)), jitter and shimmer using three software analysis systems: MDVP, PRAAT, and TF32 (CSpeech). Fifteen regression trees and their Variable Importance Measures were utilized to analyze the data. The analyses confirmed that all of the factors listed above were influential. The results suggest that gender, intrasubject variability, and microphone were significant influences on F(0). Software systems and gender were highly influential on measurements of jitter and shimmer. Environmental noise was shown to be the prominent factor that affects VQM when SNR levels are below 30 dB.

Acoustic Stimulation↗

PubMed2005

Adverse effects of environmental noise on acoustic voice quality measurements.

An accurate analysis of voice quality is imperative when using acoustic measurements to diagnose vocal pathologies. It is known that noise has a significant effect on the reliability and validity of acoustic voice measurements, but the precise relationship has not been established. The purpose of this study was to investigate the influence of noise on the accuracy, reliability, and validity of acoustic voice quality measurements while balancing for gender, age, intersubject and intrasubject variability, microphones, computer hardware, analysis software, and type of noise. Level of noise was precisely controlled. The specific focus of interest was to determine the critical levels of noise that can invalidate voice quality measurements and to generate practical recommendations. Results suggest that the recommended, acceptable, and unacceptable levels of noise in the acoustic environment are above 42 dB, above 30 dB, and below 30 dB signal-to-noise ratio, respectively.

Acoustics↗

PubMed2005

Influence of data acquisition environment on accuracy of acoustic voice quality measurements.

Accuracy of acoustic voice analysis is influenced by the quality of recording. Lately, articles have suggested that soundcards perform equivalently to specialized professional-grade data acquisition (DA) systems. The purpose of this study was to investigate the influence of DA environment (DA system and microphone) on acoustic voice quality measurement (VQM) while balancing for gender, age, intersubject and intrasubject variability, and analysis software. More specifically, the relative performance of different hardware environments and the relationship between their technical characteristics and VQM performance was investigated. The discretization error and the effective dynamic range of the different DA environments were measured. We used 3 software systems to record and measure separately 2000 acoustic samples of sustained phonation for fundamental frequency, jitter, and shimmer. Analyses of variance (ANOVA) were performed with these parameters as the dependent variables. The results of the study suggested that professional-grade DA hardware is strongly recommended to provide accurate and valid voice assessment. The fundamental frequency measurement differences across DA environments were highly correlated to the discretization error (r=1.00), whereas jitter and shimmer were highly correlated to the effective dynamic range of the DA environments (r=-0.68 and r=-0.86, respectively).

Adult↗

PubMed2005

Influence of sampling rate on accuracy and reliability of acoustic voice analysis.

It is universally recognized that sampling rate (F(S)) influences the reliability and validity of acoustic voice measurements; however, an exact relationship has not been determined. The purpose of this experiment was to investigate the influence of F(S) on acoustic voice quality measurements, while considering the influences of gender, intra-subject variability, microphone, environmental noise, data acquisition hardware, and analysis software as balancing factors. The impact of F(S), from 44.1 kHz to 10 kHz, was explored by analyzing 864,000 measures of fundamental frequency, jitter, and shimmer, using three software analysis systems: MDVP, TF32, and PRAAT. Results suggest that the recommended, acceptable, and critical F(S) for acoustic voice analysis are above 26 kHz, above 19 kHz, and 12 kHz, respectively. Thus, voice samples captured above 26 kHz can be used for data analysis and compared without introducing error due to F(S).

Acoustic Stimulation↗

PubMed2004

Endoscope motion compensation for laryngeal high-speed videoendoscopy.

The purpose of this study was to develop and evaluate a method for automatic endoscopic motion compensation (MC) specialized for laryngeal high-speed videoendoscopy (HSV) of sustained phonation. Specifically, the left-right and posterior-anterior endoscopic shifts were addressed. The method is based on the hypothesis that the difference between endoscopic and vocal fold dynamics is sufficient for accurate estimation of the endoscopic motion relative to the vocal folds. The research questions of particular interest were as follows: is MC of laryngeal HSV possible at the subpixel level, and what are the validity, reliability, and accuracy of the proposed MC method? First, the MC accuracy was assessed on simulated HSV data with exactly known motion trajectories. Then, the accuracy and reliability of MC were evaluated on real HSV data. Finally, the validity of MC was established by correlating objective to perceptual ratings. The method demonstrated subpixel accuracy and reliable performance when tested on both simulated and real data. Perceptual ratings of the endoscopic motion demonstrated high intrarater and interrater reliabilities. Perceptual and quantitative assessments of endoscopic motion were in agreement. The reported result is encouraging for resolving a persistent problem toward building better methods for visual and quantitative voice assessment.

Female↗