Perceptual and Acoustic Characteristics of Voice Changes in Reflux Laryngitis Patients

The aim of the study was to outline the multidimensional perceptual, subjective, and instrumental acoustic voice changes in the group of reflux laryngitis (RL) patients. Data of multidimensional voice assessment of 108 RL patients and 90 healthy persons of the control group were subjected to comparative analysis. A slight hoarseness according to the GRB (G-grade, R- rough, B-breathy) scale was prevailing in the RL patients group. Statistically significant difference (P < 0.001) between RL patients group and the control group was found of all voice parameters measured, with the patients having worse results--increased mean jitter, shimmer, normalized noise energy, voice handicap index (VHI), and decreased parameters of phonetogram. The results of the study demonstrated that multidimensional voice assessment documented deteriorated voice quality and restricted phonation capabilities in the tested group of RL patients.     

Categorizing Normal and Pathological Voices: Automated and Perceptual Categorization

Objectives

The aims of the present study were to evaluate the accuracy of an elaborated automated voice categorization system that classified voice signal samples into healthy and pathological classes and to compare it with classification accuracy that was attained by human experts.

Material and Methods

We investigated the effectiveness of 10 different feature sets in the classification of voice recordings of the sustained phonation of the vowel sound /a/ into the healthy and two pathological voice classes, and proposed a new approach to building a sequential committee of support vector machines (SVMs) for the classification. By applying “genetic search” (a search technique used to find solutions to optimization problems), we determined the optimal values of hyper-parameters of the committee and the feature sets that provided the best performance. Four experienced clinical voice specialists who evaluated the same voice recordings served as experts. The “gold standard” for classification was clinically and histologically proven diagnosis.

Results

A considerable improvement in the classification accuracy was obtained from the committee when compared with the single feature type-based classifiers. In the experimental investigations that were performed using 444 voice recordings coming from 148 subjects, three recordings from each subject, we obtained the correct classification rate (CCR) of over 92% when classifying into the healthy-pathological voice classes, and over 90% when classifying into three classes (healthy voice and two nodular or diffuse lesion voice classes). The CCR obtained from human experts was about 74% and 60%, respectively.

Conclusion

When operating under the same experimental conditions, the automated voice discrimination technique based on sequential committee of SVM was considerably more effective than the human experts.     

Transverse and longitudinal phase-matching in third harmonic generation induced by the Bessel beams

Influence of transverse and longitudinal phase matching on the spectral and intensity properties of third harmonic generation induced by the Bessel pump beams has been investigated both theoretically and experimentally. Transverse phase matching, revealing itself as a ring pattern in the third harmonic intensity angular spectrum was demonstrated in both the normally and anomalously dispersive media. The conditions were found for the optimization of this conical third harmonic signal.     

Perceptual and Acoustic Assessment of Voice Pathology and the Efficacy of Endolaryngeal Phonomicrosurgery

Values for acoustic voice measurements were obtained from 88 normal individuals and 98 pathological cases of mass lesions of vocal fold and 50 cases of unilateral vocal fold paralysis. Overall, all items reflecting perturbations of pitch and amplitude as well as glottal noise were significantly higher in the groups of patients compared with the normal group. The measurement of normalized noise energy (NNE) was found to be an optimum parameter for discrimination of normal/abnormal voices. The voices of patients with vocal fold nodules and vocal fold polyps were analyzed before endolaryngeal phonomicrosurgery (EPM) and 2 weeks after. Statistically significant (p < 0.01) improvement was achieved both in perceptual and acoustic analysis. EPM resulted in a significant decrease of mean jitter, shimmer, and NNE. Clinically, these measures provided documentable and measurable evidence of vocal function and were helpful for comparing patients with normal speakers. They also were useful for a thorough documentation of patient's voice pathology and for evaluation of the presurgical and postsurgical voice status.     

Phase relations between focused bichromatic laser pulses in terahertz wave generation from gas plasma

Terahertz emission from air excited by the tightly focused fundamental and second harmonic pulses of femtosecond Ti:Sapphire laser has been analyzed. It has been found that the curved phase fronts of the pump waves cancel each other resulting in the flat phase front of the nonlinear polarization at terahertz frequency. Also, in addition to the phase terms obtained using plane-wave approximation, we have found the yet unreported phase term, which in most cases can be as large as π/2.