Validation of an Algorithm for Semi-automated Estimation of Voice Relative Fundamental Frequency.

OBJECTIVES: Relative fundamental frequency (RFF) has shown promise as an acoustic measure of voice, but the subjective and time-consuming nature of its manual estimation has made clinical translation infeasible. Here, a faster, more objective algorithm for RFF estimation is evaluated in a large and diverse sample of individuals with and without voice disorders. METHODS: Acoustic recordings were collected from 154 individuals with voice disorders and 36 age- and sex-matched controls with typical voices. These recordings were split into training and 2 testing sets. Using an algorithm tuned to the training set, semi-automated RFF estimates in the testing sets were compared to manual RFF estimates derived from 3 trained technicians. RESULTS: The semi-automated RFF estimations were highly correlated ( r = 0.82-0.91) with the manual RFF estimates. CONCLUSIONS: Fast and more objective estimation of RFF makes large-scale RFF analysis feasible. This algorithm allows for future work to optimize RFF measures and expand their potential for clinical voice assessment.

Relative Fundamental Frequency Distinguishes Between Phonotraumatic and Non-Phonotraumatic Vocal Hyperfunction.

Purpose: The purpose of this article is to examine the ability of an acoustic measure, relative fundamental frequency (RFF), to distinguish between two subtypes of vocal hyperfunction (VH): phonotraumatic (PVH) and non-phonotraumatic (NPVH). Method: RFF values were compared among control individuals with typical voices (N = 49), individuals with PVH (N = 54), and individuals with NPVH (N = 35). Results: Offset Cycle 10 RFF differed significantly among all 3 groups with values progressively decreasing for controls, individuals with NPVH, and individuals with PVH. Individuals with PVH also had lower Offset Cycles 8 and 9 relative to the other 2 groups and lower RFF values for Offset Cycle 7 relative to controls. There was also a trend for lower Onset Cycle 1 RFF values for the PVH group compared with the NPVH group. Conclusions: RFF values were significantly different between controls and individuals with VH and also between the two subtypes of VH. This study adds further support to the notion that the differences between these two subsets of VH may be functional as well as structural.

The Relationship Between Relative Fundamental Frequency and a Kinematic Estimate of Laryngeal Stiffness in Healthy Adults.

Purpose: This study examined the relationship between the acoustic measure relative fundamental frequency (RFF) and a kinematic estimate of laryngeal stiffness. Method: Twelve healthy adults (mean age = 22.7 years, SD = 4.4; 10 women, 2 men) produced repetitions of /ifi/ while varying their vocal effort during simultaneous acoustic and video nasendoscopic recordings. RFF was determined from the last 10 voicing cycles before the voiceless obstruent (RFF offset) and the first 10 cycles of revoicing (RFF onset). A kinematic stiffness ratio was calculated for the vocal fold adductory gesture during revoicing by normalizing the maximum angular velocity by the maximum glottic angle during the voiceless obstruent. Results: A linear mixed effect model indicated that RFF offset and onset were significant predictors of the kinematic stiffness ratios. The model accounted for 52% of the variance in the kinematic data. Individual relationships between RFF and kinematic stiffness ratios varied across participants, with at least moderate negative correlations in 83% of participants for RFF offset but only 40% of participants for RFF onset. Conclusions: RFF significantly predicted kinematic estimates of laryngeal stiffness in healthy speakers and has the potential to be a useful clinical indicator of laryngeal tension. Further research is needed in individuals with voice disorders.

Objective Measure of Nasal Air Emission Using Nasal Accelerometry.

Purpose: This article describes the development and initial validation of an objective measure of nasal air emission (NAE) using nasal accelerometry. Method: Nasal acceleration and nasal airflow signals were simultaneously recorded while an expert speech language pathologist modeled NAEs at a variety of severity levels. In addition, microphone and nasal accelerometer signals were collected during the production of /pɑpɑpɑpɑ/ speech utterances by 25 children with and without cleft palate. Fourteen inexperienced raters listened to the microphone signals from the pediatric speakers and rated the samples for the severity of NAE using direct magnitude estimation. Mean listener ratings were compared to a novel quantitative measurement of NAE derived from the nasal acceleration signals. Results: Correlation between the nasal acceleration energy measure and the measured nasal airflow was high (r = .87). Correlation between the measure and auditory-perceptual ratings was moderate (r = .49). Conclusion: The measure presented here is quantitative and noninvasive, and the required hardware is inexpensive ($150). Future studies will include speakers with a wider range of NAE severity and etiology, including cleft palate, hearing impairment, or dysarthria. Further development will also involve validation of the measure against airflow measures across subjects.

Colchicine derivative as a potential anti-glioma compound.

Colchicine, an anti-microtubule and antimitotic drug, is a common therapeutically agent for gout, which is thought to have potential anti-tumor effects. Owing to concerns of colchicines poisoning, the development of derivatives with low dose efficacy and less side effects is of obvious interest. In this study, we characterized the inhibitory effects of a colchicine derivative named AD1 on the cell proliferation of human malignant glioblastoma (MG) cell lines, U87MG and U373MG. We found that 50 % of U87MG and U373MG cells were reduced in the cultures after exposure to AD1 for 24 h at 10 and 50 nM, respectively. Moreover, α-tubulin immunostaining indicated that AD1 induced the disruption of the microtubule polymerization in glioma cells with apoptotic features including membrane budding/blebbing or fragmented nuclei. Increased levels of reactive oxygen species (ROS) were also detected in AD1-treated U87MG and U373MG cells compared to that observed in the control culture. Moreover, examination of microtubule-associated protein 1A/1B-light chain 3 (LC3I)/LC3II conversion and acridine orange staining for autophagic vesicles, combined with flow cytometry, showed that treatment with AD1 induced the autophagic pathway in U87MG and U373MG cells. Furthermore, we found that the intermittent intravenous administration of AD1 suppressed glioma growth in rat brain receiving intracerebral injection with rat C6 glioma cells. Taken together, our findings reveal that treatment with AD1 at nanomolar scales can reduce glioma cell viability effectively, with the occurrence of a rise in ROS and cellular autophagy. In conjunction with the observations from in vivo study, the colchicine derivative AD1 has chemotherapeutic potential to suppress glioma progression.

Voice Relative Fundamental Frequency Via Neck-Skin Acceleration in Individuals With Voice Disorders.

PURPOSE: This study investigated the use of neck-skin acceleration for relative fundamental frequency (RFF) analysis. METHOD: Forty individuals with voice disorders associated with vocal hyperfunction and 20 age- and sex-matched control participants were recorded with a subglottal neck-surface accelerometer and a microphone while producing speech stimuli appropriate for RFF. Rater reliabilities, RFF means, and RFF standard deviations derived from the accelerometer were compared with those derived from the microphone. RESULTS: RFF estimated from the accelerometer had slightly higher intrarater reliability and identical interrater reliability compared with values estimated with the microphone. Although sensor type and the Vocal Cycle × Sensor and Vocal Cycle × Sensor × Group interactions showed significant effects on RFF means, the typical RFF pattern could be derived from either sensor. For both sensors, the RFF of individuals with vocal hyperfunction was lower than that of the controls. Sensor type and its interactions did not have significant effects on RFF standard deviations. CONCLUSIONS: RFF can be reliably estimated using an accelerometer, but these values cannot be compared with those collected via microphone. Future studies are needed to determine the physiological basis of RFF and examine the effect of sensors on RFF in practical voice assessment and monitoring settings.

Individual Monitoring of Vocal Effort With Relative Fundamental Frequency: Relationships With Aerodynamics and Listener Perception.

PURPOSE: The acoustic measure relative fundamental frequency (RFF) was investigated as a potential objective measure to track variations in vocal effort within and across individuals. METHOD: Twelve speakers with healthy voices created purposeful modulations in their vocal effort during speech tasks. RFF and an aerodynamic measure of vocal effort, the ratio of sound pressure level to subglottal pressure level, were estimated from the aerodynamic and acoustic signals. Twelve listeners also judged the speech samples for vocal effort using the visual sort and rate method. RESULTS: Relationships between RFF and both the aerodynamic and perceptual measures of vocal effort were weak across speakers (R2 = .06-.26). Within speakers, relationships were variable but much stronger on average (R2 = .45-.56). CONCLUSIONS: RFF showed stronger relationships between both the aerodynamic and perceptual measures of vocal effort when examined within individuals versus across individuals. Future work is necessary to establish these relationships in individuals with voice disorders across the therapeutic process.

Comparison of voice relative fundamental frequency estimates derived from an accelerometer signal and low-pass filtered and unprocessed microphone signals.

The relative fundamental frequency (RFF) surrounding the production of a voiceless consonant has previously been estimated using unprocessed and low-pass filtered microphone signals, but it can also be estimated using a neck-placed accelerometer signal that is less affected by vocal tract formants. Determining the effects of signal type on RFF will allow for comparisons across studies and aid in establishing a standard protocol with minimal within-speaker variability. Here RFF was estimated in 12 speakers with healthy voices using unprocessed microphone, low-pass filtered microphone, and unprocessed accelerometer signals. Unprocessed microphone and accelerometer signals were recorded simultaneously using a microphone and neck-placed accelerometer. The unprocessed microphone signal was filtered at 350 Hz to construct the low-pass filtered microphone signal. Analyses of variance showed that signal type and the interaction of vocal cycle × signal type had significant effects on both RFF means and standard deviations, but with small effect sizes. The overall RFF trend was preserved regardless of signal type and the intra-speaker variability of RFF was similar among the signal types. Thus, RFF can be estimated using either a microphone or an accelerometer signal in individuals with healthy voices. Future work extending these findings to individuals with disordered voices is warranted.

Effects of phonetic context on relative fundamental frequency.

PURPOSE: The effect of phonetic context on relative fundamental frequency (RFF) was examined, in order to develop stimuli sets with minimal within-speaker variability that can be implemented in future clinical protocols. METHOD: Sixteen speakers with healthy voices produced RFF stimuli. Uniform utterances consisted of 3 repetitions of the same voiced sonorant-voiceless consonant-voiced sonorant speech sequence; moderately variable sentences contained speech sequences with a single voiceless phoneme (/f/, /s/, /ʃ/, /p/, /t/, or /k/); highly variable sentences were loaded with speech sequences using multiple phonemes. Effects of stimulus type (uniform, moderately variable, and highly variable) and phoneme identity (/f/, /s/, /ʃ/, /p/, /t/, and /k/) on RFF means and standard deviations were determined. RESULTS: Stimulus type and the interaction of vocal cycle and stimulus type were significant for RFF means and standard deviations but with small effect sizes. Phoneme identity and the interaction of vocal cycle and phoneme identity on RFF means and standard deviations were also significant with small to medium effect sizes. CONCLUSIONS: For speakers with healthy voices, uniform utterances with /f/ and /ʃ/ have the lowest standard deviations and thus are recommended for RFF-based assessments. Future work is necessary to extend these findings to disordered voices.

Automated estimation of relative fundamental frequency.

Relative fundamental frequency (RFF), defined as the normalized fundamental frequencies of vowels surrounding voiceless consonants, has been shown to have a characteristic pattern in healthy voices that differs from those with disordered voices (e.g. vocal hyperfunction, Parkinson's disease). However no large-scale clinical study has been performed, mainly because the current estimation protocol requires trained technicians to manually perform this time-consuming task. In this study, we developed a method to automate RFF estimation and tested the algorithm on recordings from 12 healthy participants and 12 participants with Parkinson's disease. The means and variations of RFFs estimated using the automation algorithm were similar to the 'gold standard' estimates developed by two trained technicians. The mean squared error for the automated estimates, when compared to the 'gold standard' RFF estimates, were similar to those estimated manually by an additional trained technician. Future work will focus on improving vocal cycle detection and extending the automation to estimate RFF from instances in running speech.