Harmonics-to-noise ratio estimation with deterministically time-varying harmonic model for pathological voice signals

A Chaotic Approach to Glottal Gap Voice

OBJECTIVE

Airway glottic insufficiency, or glottal gap, may lead to a breathy voice quality. It is hypothesized that a glottal gap may be a source of nonlinearity in speech production. This study aims to gain a chaotic and acoustic profile of glottal gap voice provided by phonation of excised larynges subjected to the insertion of a metal shim in the posterior glottis.

STUDY DESIGN

Nonrandomized quasi-experimental study.

METHODS

Posterior glottal gap varied from 0 to 3.5 mm in 0.5 mm intervals. Each treatment was investigated independently in a sample population of eight excised canine larynges. Phonation of the larynges for each treatment was recorded and analyzed for the cepstral peak prominence (CPP), harmonics-to-noise ratio (HNR), and correlation dimension.

RESULTS

Kruskal-Wallis rank-sum tests yielded significant differences across shim groups for all parameters. Dunn-Bonferroni post-hoc tests revealed that the control group differed significantly from the 1.5, 2, 2.5, 3, and 3.5 mm groups for all metrics. Moreover, Kendall correlation tests indicated a moderately positive correlation between glottal gap size and correlation dimension, a moderately negative correlation between glottal gap size and CPP and between glottal gap size and the HNR.

CONCLUSIONS

Glottic insufficiency provides a source of nonlinearity in phonation. Nonlinear dynamic analysis provides quantitative insight into glottal gap voice. This study encourages future studies to further evaluate the relationship between glottal gap and correlation dimension.

Effect of Wearing Different Masks on Acoustic, Aerodynamic, and Formant Parameters

OBJECTIVE

This study aimed to investigate the effects of different types of masks on acoustic, aerodynamic, and formant parameters in healthy people.

METHODS

Our study involved 30 healthy participants, 15 of each gender, aged 20-40 years. The tests were conducted under four conditions: without a mask, after wearing a surgical mask, after wearing a head-mounted N95 mask, and after wearing an ear-mounted N95 mask. Voice recording was done with the mask on. The acoustic parameters include mean fundamental frequency (F0), mean intensity, percentage of jitter (local), percentage of shimmer (local), mean noise to harmonic ratio (NHR), aerodynamic parameter, maximum phonation time (MPT), and formant parameters (/a/, /i/, /u/ three vowels F1, F2).

RESULTS

The main effect of mask type was significant in MPT, mean F0, mean HNR, /a/F1, /a/F2, /i/F2. However, the effect sizes and power in /a/F2, /i/F2 were low. MPT, mean F0 and mean HNR significantly increased and /a/F1 significantly decreased after wearing the head-mounted n95 mask. The mean F0 and mean HNR increased significantly after wearing the ear-mounted n95 mask. No significant changes were observed in parameters after wearing the surgical mask in this study. When the statistics are performed separately for males and females, the results obtained are similar to those previously obtained for unspecified males and females.

CONCLUSION

After wearing the surgical mask, this study found insignificant changes in mean F0, jitter (local), shimmer (local), mean NHR, mean intensity, MPT, and the vowels F1 and F2. This may be due to the looser design of the surgical mask and the relatively small attenuation of sound. N95 masks have a greater effect on vocalization than surgical masks and may cause changes in F0 and HNR after wearing an N95 mask. In the present study, no significant changes in jitter and shimmer were observed after wearing the mask. In addition, there was a significant reduction in /a/F1 after wearing the N95 headgear mask may owing to its high restriction of jaw mobility. In future studies, the change in jaw movement amplitude after wearing the mouthpiece can be added to investigate.

Work-Related Vocal Challenges of Online Teaching: A Study of Female College Professors

BACKGROUND

College professors are at an elevated risk of developing voice disorders due to increased vocal demands associated with their working conditions, including high background noise levels, long reverberation times, prolonged voice use duration, and large class sizes. However, the impact of online classes on vocal health among college professors remains unclear.

OBJECTIVE

This longitudinal study aimed to characterize voice changes associated with online teaching among female Colombian college professors.

METHODS

Thirteen female college professors teaching online classes completed an online survey that included questions about voice functioning, working conditions, the Spanish translation of the Vocal Fatigue Index (VFI), and the Spanish translation of the Voice-Related Quality of Life. Instrumental measurements were also performed, including environmental background noise levels, hearing screening, and voice recordings before and after a synchronous online class.

RESULTS

This study found a decreased fundamental frequency in connected speech (reading) associated with the number of students per class, the number of classes per week, and background noise levels measured with a sound level meter. L1L0 was statistically smaller among experienced teachers with higher background noise levels compared with less-experienced colleagues in quieter classes. 1558kHz was statistically associated with the average number of students, whereas HNR was slightly higher for professors with more students and more classes per week.

CONCLUSION

The findings suggest that online teaching has important implications for voice production among participating teachers. This study highlights the importance of considering working conditions during online classes when designing workplace prevention programs for college professors.

Formant-Aware Spectral Analysis of Sustained Vowels of Pathological Breathy Voice

OBJECTIVES

This paper reports the effectiveness of formant-aware spectral parameters to predict the perceptual breathiness rating. A breathy voice has a steeper spectral slope and higher turbulent noise than a normal voice. Measuring spectral parameters of acoustic signals over lower formant regions is a known approach to capture the properties related to breathiness. This study examines this approach by testing the contemporary spectral parameters and algorithms within the framework, alternate frequency band designs, and vowel effects.

METHODS

Sustained vowel recordings (/a/, /i/, and /u/) of speakers with voice disorders in the German Saarbrueken Voice Database were considered (n: 367). Recordings with signal irregularities, such as subharmonics or with roughness perception, were excluded from the study. Four speech language pathologists perceptually rated the recordings for breathiness on a 100-point scale, and their averages were used in the analysis. The acoustic spectra were segmented into four frequency bands according to the vowel formant structures. Five spectral parameters (intraband harmonics-to-noise ratio, HNR; interband harmonics ratio, HHR; interband noise ratio, NNR; and interband glottal-to-noise energy, GNE, ratio) were evaluated in each band to predict the perceptual breathiness rating. Four HNR algorithms were tested.

RESULTS

Multiple linear regression models of spectral parameters, led by the HNRs, were shown to explain up to 85% of the variance in perceptual breathiness ratings. This performance exceeded that of the acoustic breathiness index (82%). Individually, the HNR over the first two formants best explained the variances in the breathiness (78%), exceeding the smoothed cepstrum peak prominence (74%). The performance of HNR was highly algorithm dependent (10% spread). Some vowel effects were observed in the perceptual rating (higher for /u/), predictability (5% lower for /u/), and model parameter selections.

CONCLUSIONS

Strong per-vowel breathiness acoustic models were found by segmenting the spectrum to isolate the portion most affected by breathiness.