Effects of low-pass filtering on acoustic analysis of voice.

OBJECTIVE/HYPOTHESIS: Low-pass filtering is often applied to eliminate effects of environmental noise when preparing voice recordings for acoustic analysis. This study tested the effects of low-pass filter cutoff frequency on the results of acoustic voice analysis, with a particular interest in the effects of low cutoff frequencies on nonlinear dynamic parameters. STUDY DESIGN: A crossover randomized controlled trial was performed using voice recordings of sustained vowel phonation obtained from the Disordered Voice Database. METHODS: A second-order Butterworth filter was applied to the voices at cutoff frequencies ranging from 5000 to 40 Hz. Percent jitter, percent shimmer, fundamental frequency (F(0)), signal-to-noise ratio (SNR), correlation dimension (D(2)), and second-order entropy (K(2)) were calculated for each signal. RESULTS: Traditional acoustic parameters were validly measured at cutoff frequencies as low as 300 Hz. The SNR and percent shimmer were improved by cutoff frequencies of 300 Hz or higher; F(0) and percent jitter were unaffected by filtering at these frequencies. D(2) and K(2) were measured stably for signals filtered at cutoff frequencies as low as 100 Hz. CONCLUSION: To ensure accuracy in acoustic voice analysis, setting the cutoff frequency of a low-pass filter at least one octave above the F(0) (minimum of 300 Hz) is recommended. Nonlinear dynamic measures of D(2) and K(2) proved more robust and maintained accuracy at lower frequencies.

Vowel selection and its effects on perturbation and nonlinear dynamic measures.

OBJECTIVE: Acoustic analysis of voice is typically conducted on recordings of sustained vowel phonation. This study applied perturbation and nonlinear dynamic analyses to the vowels /a/, /i/, and /u/ in order to determine vowel selection effects on analysis. PATIENTS AND METHODS: Forty subjects (20 males and 20 females) with normal voices participated in recording. Traditional parameters of fundamental frequency, signal-to-noise ratio, percent jitter, and percent shimmer were calculated for the signals using CSpeech. Nonlinear dynamic parameters of correlation dimension and second-order entropy were also calculated. RESULTS: Perturbation analysis results were largely incongruous in this study and in previous research. Fundamental frequency results corroborated previous work, indicating higher fundamental frequency for /i/ and /u/ and lower fundamental frequency for /a/. Signal-to-noise ratio results showed that /i/ and /u/ have greater harmonic levels than /a/. Results of nonlinear dynamic analysis suggested that more complex activity may be evident in /a/ than in /i/ or /u/. CONCLUSION: Percent jitter and percent shimmer may not be useful for description of acoustic differences between vowels. Fundamental frequency, signal-to-noise ratio, and nonlinear dynamic parameters may be applied to characterize /a/ as having lower frequency, higher noise, and greater nonlinear components than /i/ and /u/.

Effects of the Voice over Internet Protocol on perturbation analysis of normal and pathological phonation.

OBJECTIVE: In this study, a Voice over Internet Protocol (VoIP) communication based on G.729 protocol was simulated to determine the effects of this system on acoustic perturbation parameters of normal and pathological voice signals. PATIENTS AND METHODS: Fifty recordings of normal voice and 48 recordings of pathological voice affected by laryngeal paralysis were transmitted through a VoIP communication system. The acoustic analysis programs of CSpeech and MDVP were used to determine the percent jitter and percent shimmer from the voice samples before and after VoIP transmission. The effects of three frequently used audio compression protocols (MP3, WMA, and FLAC) on the perturbation measures were also studied. RESULTS: It was found that VoIP transmission disrupts the waveform and increases the percent jitter and percent shimmer of voice samples. However, after VoIP transmission, significant discrimination between normal and pathological voices affected by laryngeal paralysis was still possible. It was found that the lossless compression method FLAC does not exert any influence on the perturbation measures. The lossy compression methods MP3 and WMA increase percent jitter and percent shimmer values. CONCLUSION: This study validates the feasibility of these transmission and compression protocols in developing remote voice signal data collection and assessment systems.

Transoral laser surgery for anterior commissure involvement: a study in canines.

OBJECTIVE: To present laser surgery techniques to address anterior commissure involvement and evaluate recovery. METHODS: Twelve canines were divided into three groups. In group A the right ventricular band and vocal fold, the anterior third of the left vocal fold, and anterior commissure were cauterized. In group B cauterization was extended to the thyroid cartilage and a 5 mm x 5 mm area of the anterior commissural to half the cartilage thickness. In group C the 5 mm x 5 mm window was extended through the thyroid cartilage. Surgical lesions were observed after surgery and at 1 and 4 weeks post-surgery. RESULTS: Post-operative gross examination confirmed target scopes. One week after surgery, the lesions in group A were completely covered by neo-mucosa, while group B and C wounds were only partially covered. After 4 weeks, a laryngeal web was seen at the anterior commissure and the vocal fold length was shortened. Lesions in all three groups were completely covered by neo-mucosa. Collagen proliferation was most prominent in group C with limited scarring in group A. There were no major complications. CONCLUSIONS: The three operative methods demonstrated satisfactory outcomes; the lesions recovered well over the course of 4 weeks, and no severe complications occurred. The laser surgery protocol was successfully extended into the thyroid cartilage.

Acoustic analysis of the tremulous voice: assessing the utility of the correlation dimension and perturbation parameters.

UNLABELLED: Acoustic analysis may provide a useful means to quantitatively characterize the tremulous voice. Signals were obtained from 25 subjects with diagnoses of either Parkinson's disease or vocal polyps exhibiting vocal tremor. These were compared to signals from 24 subjects with normal voices. Signals were analyzed via correlation dimension and several parameters from the Multi-Dimensional Voice Program (MDVP): percent jitter, percent shimmer, amplitude tremor intensity index (ATRI), frequency tremor intensity index (FTRI), amplitude tremor frequency (Fatr), and fundamental frequency tremor frequency (Fftr). No significant difference was found between the tremor and control groups for ATRI and Fatr. Percent jitter, percent shimmer, FTRI, Fftr, and correlation dimension values were found to be significantly higher in the tremor group than in the control group. We conclude that these parameters may have utility for the clinical quantification of tremor severity and treatment effects. LEARNING OUTCOMES: The reader will understand the utility of applying select perturbation parameters and the nonlinear measure of correlation dimension for the characterization of the tremulous voice.

Primary treatment of acute dacryocystitis by endoscopic dacryocystorhinostomy with silicone intubation guided by a soft probe.

PURPOSE: To investigate the suitability of cold steel endonasal endoscopic dacryocystorhinostomy (EES-DCR) with circular bicanalicular intubation with silicone tubes (CBIST) guided by a soft probe for the primary treatment of acute purulent dacryocystitis (APD). DESIGN: Prospective, randomized, interventional case series. PARTICIPANTS: Seventy-two patients (59 females, 13 males) with a median presenting age of 55+/-12 years (range, 28-71 years). METHODS: Eighty-four patients with unilateral APD were equally and randomly divided into 2 groups. Cold steel EES-DCR was performed after the lacrimal abscess formation, and external dacryocystorhinostomy (E-DCR) was performed 1 to 2 weeks after resolution of the acute inflammation. In both groups, CBIST guided by a soft probe was performed and the silicone tubes were kept in the lacrimal passages for 3 months. Postoperative follow-up ranged from 12 to 24 months. Outcomes were compared between both groups, considering resolution time for external acute inflammation, success rate of free lacrimal passage reconstruction, and lack of complications as indicators of treatment suitability. MAIN OUTCOME MEASURES: Time for resolution of the external acute inflammation, success rate of free lacrimal passage reconstruction, and complications. RESULTS: In this study, complete postoperative data were acquired from 40 patients in the EES-DCR group and from 32 patients in the E-DCR group, and the outcomes were compared. Acute inflammation resolved more quickly in the EES-DCR group than in the E-DCR group (P<0.05). Ostium patency at 12 months after silicone tube removal was achieved in significantly more patients in the EES-DCR group (36/40 [90%]) than in the E-DCR group (21/32 [65.7%]; P<0.01). In the EES-DCR group, lacrimal passage reconstruction failed because of intranasal ostial closure in 3 patients and because of common canaliculus obstruction in 1 patient. In the E-DCR group, lacrimal passage reconstruction failed because of intranasal ostial closure in 3 patients, lacrimal sac fibrosis, granulation, or both in 6 patients, and common canaliculus obstruction in 2 patients. Other than the slight laceration of the inferior puncta, no significant complications arose from the treatments. CONCLUSIONS: Cold steel EES-DCR with CBIST guided by a soft probe is a promising alternative for the primary treatment of APD with abscess formation. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any materials discussed in this article.

Acoustic analysis of aperiodic voice: perturbation and nonlinear dynamic properties in esophageal phonation.

Esophageal voice is a method of voice production after total laryngectomy. Previous research suggests that perturbation analysis may inaccurately measure aperiodic voices and that nonlinear dynamic methods may be more appropriate for analyzing signals of this type. Therefore, we hypothesized that nonlinear dynamic analysis would be more capable than perturbation parameters for reliable measurement of the aperiodic esophageal voice. The study design was acoustic comparison of esophageal and normal voice cohorts using nonlinear dynamic and perturbation measures. Twenty subjects in two age-matched groups participated in the study. Jitter, shimmer, signal-to-noise ratio (SNR), correlation dimension, and second-order entropy were measured from audio recordings of subjects' voices. Jitter and shimmer values were significantly higher and SNR values were significantly lower for esophageal voices than for normal voices. Error (err) count values, which indicate perturbation analysis reliability, were 0 in normal voices and significantly higher in esophageal voices. Error was attributable to signal aperiodicity and demonstrated that perturbation analysis yielded questionable results for esophageal voice. However, nonlinear dynamics measures analyzed both cohorts reliably and indicated that esophageal voice was significantly more chaotic than normal voice. The results demonstrated the capability of nonlinear dynamic methods to reliably quantify both aperiodic and periodic signals and differentiate normal from esophageal voices. It is suggested that nonlinear dynamic analysis be used preferentially for acoustic characterization of aperiodic voices, such as esophageal voice. Future research should focus on clarification of perturbation analysis reliability and further application of nonlinear dynamic measures to aperiodic voices.

Quantifying the complexity of excised larynx vibrations from high-speed imaging using spatiotemporal and nonlinear dynamic analyses.

In this paper, we investigate the biomechanical applications of spatiotemporal analysis and nonlinear dynamic analysis to quantitatively describe regular and irregular vibrations of twelve excised larynges from high-speed image recordings. Regular vibrations show simple spatial symmetry, temporal periodicity, and discrete frequency spectra, while irregular vibrations show complex spatiotemporal plots, aperiodic time series, and broadband spectra. Furthermore, the global entropy and correlation length from spatiotemporal analysis and the correlation dimension from nonlinear dynamic analysis reveal a statistical difference between regular and irregular vibrations. In comparison with regular vibrations, the global entropy and correlation dimension of irregular vibrations are statistically higher, while the correlation length is significantly lower. These findings show that spatiotemporal analysis and nonlinear dynamic analysis are capable of describing the complex dynamics of vocal fold vibrations from high-speed imaging and may potentially be helpful for understanding disordered behaviors in biomedical laryngeal systems.