Effect of Voice Onset Type on Vocal Attack Time.

Vocal attack time (VAT) is the time lag between the growth of sound pressure (SP) and electroglottographic (EGG) signals at vocal initiation. The characteristics of voice initiation are associated with issues of vocal hygiene, efficiency, and quality. Vocal onsets have commonly been qualitatively characterized into three types: hard, simultaneous, and breathy. This study examines the effect of voice onset type on VAT values in normal speakers. SP and EGG recordings were obtained for 55 female and 57 male subjects while producing multiple tokens of three tasks (sustained /ɑ/ and "always" as unaspirated onsets, and "hallways" as an aspirated onset). Results revealed a significant effect of onset type on VAT, with the mean VAT for the "hallways" (aspirated) task greater than the mean VAT for the sustained /ɑ/ and "always" (unaspirated) tasks. There was no significant VAT difference between the sustained /ɑ/ and "always" tasks. Findings confirm the sensitivity of the VAT measure to vocal onset type and suggest its potential application as an objective and quantitative clinical measure of the type of vocal onset.

Comparison of trans-nasal laryngoscopic office based biopsy of laryngopharyngeal lesions with traditional operative biopsy.

The objectives of this study are to compare the pathological results from office-based biopsy (OBB) and operative biopsy (ORB) of laryngopharyngeal lesions from 26 patients. Lesion location, specimen concordance, efficacy, cost savings, and patient management are discussed. OBB can provide a sample of laryngopharyngeal tissue that can be used to diagnose lesions in these sites. This study design is retrospective review and involved retrospective analysis and chart review of 26 cases of patients who had an OBB followed by and ORB of the same site; oropharyngeal or laryngopharyngeal lesion. CPT 31576 was to identify patients. Twenty six patients had both OBB and operative biopsy performed of a lesion within the oropharynx and laryngopharynx. All OBB attempts resulted in diagnostic tissue samples. Vocal fold biopsy (69 %) was most common. The most common OBB diagnosis was squamous cell carcinoma or moderate-to-severe dysplasia (54 %). OBB and ORB pathological results were the same in 81 % of patients. Of the benign samples obtained by OBB, 83 % of the ORB were deemed benign. Of the non-benign samples obtained via OBB, 80 % of the ORB were deemed non-benign in the operating room samples. Office-based biopsy is a simple procedure that can be performed in an outpatient setting, avoiding an operating room and the need for general anesthesia. Comparison of results from OBB to ORB together with patient characteristics resulted in very reliable results that can help to guide further patient management.

Effect of fundamental frequency at voice onset on vocal attack time.

OBJECTIVE: To examine vocal attack time (VAT) values associated with the production of low, mid, and high rates of vocal fold vibration in normal speakers. STUDY DESIGN: Sound pressure (SP) and electroglottographic (EGG) recordings were obtained for eight female and five male subjects while producing multiple tokens of the sustained vowels /ɑ/, /i/, and /u/ at comfortable loudness and at mid, low (-3 semitones), and high (+6 semitones) rates of vocal fold vibration. METHODS: Generalized sinusoidal models of the SP and EGG signals were computed to compare rates of amplitude change. VAT was computed from the time lag of the cross-correlation function. RESULTS: Adjusted mean VAT for the high frequency condition was smaller than the adjusted mean VAT values for the low- and mid-frequency conditions. There was no significant difference between the mid and low frequency conditions. CONCLUSIONS: Findings reveal an association of the VAT measure with increases in vocal fold tension associated with the production of high rates of vocal fold vibration.

Vocal release time: a quantification of vocal offset.

OBJECTIVE: To determine the vocal release time (VRT) for linguistically unconstrained voice offsets in a healthy young adult population. STUDY DESIGN: Sound pressure (SP) and electroglottographic (EGG) recordings were obtained for 57 female and 55 male subjects while producing multiple tokens of three tasks (sustained /ɑ:/, "always," and "hallways") at comfortable pitch and loudness. METHODS: SP and EGG signals were digitally time reversed and generalized sinusoidal models of the SP and EGG signals were obtained to compare rates of amplitude change. VRT was computed from the time lag of the cross-correlation function. RESULTS: Adjusted mean VRT values were significantly greater for females than for males. There was no systematic effect of age on VRT. However, 25-29-year old and >40 year old females showed shorter VRT values than the youngest female age group. CONCLUSIONS: Normative data are presented for a new measure of the duration of vocal offset, VRT. Acquisition of this measure requires little user intervention, thereby minimizing effects of subjective decision making. Comparison with previously reported vocal attack time (VAT) values for the same population suggests phenomenological differences between linguistically and physiologically constrained voice onsets and unconstrained voice offsets.

Effect of tones on vocal attack time in Cantonese speakers.

Vocal attack time (VAT) is the time lag between the growth of the sound pressure signal and the development of physical contact of vocal folds at vocal initiation. It can be derived by a cross-correlation of short-time amplitude changes occurring in the sound pressure and electroglottographic (EGG) signals. Cantonese is a tone language in which tone determines the lexical meaning of the syllable. Such linguistic function of tone has implications for the physiology of tone production. The aim of the present study was to investigate the possible effects of Cantonese tones on VAT. Sound pressure and EGG signals were simultaneously recorded from 59 native Cantonese speakers (31 females and 28 males). The subjects were asked to read aloud 12 disyllabic words comprising homophone pairs of the six Cantonese lexical tones. Results revealed a gender difference in VAT values, with the mean VAT significantly smaller in females than in males. There was also a significant difference in VAT values between the two tone categories, with the mean VAT values of the three level tones (tone 1, 3, and 6) significantly smaller than those of the three contour tones (tone 2, 4, and 5). The findings support the notion that norms and interpretations based on nontone European languages may not be directly applied to tone languages.

A figure of merit for vocal attack time measurement.

OBJECTIVES: To develop and evaluate a figure of merit (FOM) for the measurement of vocal attack time (VAT) for sustained /a/. The FOM assesses a critical assumption of vocal startup on which the VAT measure is based and therefore represents integrity of the derived measure. METHODS: Pearson's correlation coefficient (0 ≤ |r| ≤ 1) was determined from amplitude features of sound pressure (SP) and electroglottographic (EGG) signals (n=1,033 tokens) to serve as a candidate FOM for the study. SP and EGG signals from 102 tokens were visually inspected to empirically derive a criterion level of FOM less than 0.75 to indicate when an assumption underlying a measurement had failed and the VAT measure should be disregarded. RESULTS: The median FOM value for all 1,033 tokens was 0.975. Thirty-two tokens (2.8%) were rejected on the basis of the FOM criterion. There was no correlation between VAT and FOM. CONCLUSIONS: A companion metric, Pearson's r, can be readily obtained to assess the quality of VAT measurement. Decisions to retain or disregard VAT measures may therefore be made on the basis of measurement quality rather than on the basis of group statistics.

Measures of vocal attack time for healthy young adults.

OBJECTIVE: To determine the vocal attack time (VAT) in a healthy young adult population. STUDY DESIGN: Sound pressure (SP) and electroglottographic (EGG) recordings were obtained for 57 female and 55 male subjects while performing multiple tokens of three tasks (sustained /a/, "always," and "hallways") at comfortable pitch and loudness. METHODS: Generalized sinusoidal models were obtained for SP and EGG signals to compare rates of amplitude change. VAT was computed from the time lag of the cross-correlation function using a fully automated process accompanied by operator validation. RESULTS: Adjusted mean VAT values were significantly shorter for females than for males. There was no systematic effect of age on VAT. However, 25- to 29-year-old men showed longer VAT than did the other age and sex subgroups. CONCLUSIONS: Normative data are presented for a new measure of the duration of vocal initiation, VAT. Acquiring this measure requires very little intervention by the user and, thereby, eliminates the influence of subjective decision making. Although beyond the scope of this article, we suggest several factors that might underlie VAT as a function of speaker sex and age.

Electromyographic and histologic evolution of the recurrent laryngeal nerve from transection and anastomosis to mature reinnervation.

OBJECTIVES: To describe the natural evolution of recurrent laryngeal nerve (RLN) reinnervation in an animal model. STUDY DESIGN: Twenty Sprague Dawley rats underwent unilateral RLN transection and anastomosis. Animals were sacrificed at 4, 8, 12, 16, and 20 weeks. Prior to sacrifice, each rat underwent electromyography (EMG) and visual grading of vocal fold motion. Bilateral RLNs were harvested and evaluated histologically. RESULTS: EMG revealed synkinetic reinnervation at all time periods except at 4 weeks. EMG evolution plateaued at 16 weeks. Vocal fold motion was slight in three rats at 4 weeks but was otherwise absent except for one rat at 12 weeks. Histologic changes of the axons and their myelin sheaths were consistent at each time period. At 16 weeks, histologic changes plateaued. CONCLUSIONS: Consistent EMG, histologic, and vocal fold motion changes occur at specific time periods during RLN reinnervation after transection and anastomosis in a rat model. Reinnervation is mature at 16 weeks. Findings corroborate theories of preferential and synkinetic reinnervation after RLN transection. Use of a rat model to investigate the effect of interventions on RLN reinnervation requires a minimum of 16 weeks between transection and investigation to allow for maturation of reinnervation.

Hand construction of quadrifilar wire electrodes for electromyography.

Array electrodes have become increasingly popular for making surface and indwelling electromyographic (EMG) recordings. We describe a method for in-house construction of indwelling quadrifilar fine-wire electrodes. Quadrifilar electrodes facilitate the mapping of vector myoelectric signatures of motoneuron firing activities of the motor nucleus, a procedure referred to as EMG decomposition. The finished electrode has four detectors, each 50 mum in diameter, arranged in a rhombus pattern. Motor unit recruitment and firing information are aids to better understanding control deficits and behaviors evidenced in the final common pathway of the central nervous system.

Observations of recurrent laryngeal nerve injury and recovery using a rat model.

OBJECTIVES/HYPOTHESIS: To evaluate standardized recurrent laryngeal nerve (RLN) injuries using a rat model via minimally invasive transoral electromyography (ToL EMG) and histologic studies. METHODS: Forty-two female Sprague Dawley rats weighing 200 g to 250 g underwent crush injury to the right RLN using a calibrated pressure clip (0.61 N or 1.19 N) for 60 seconds. Following injury, serial ToL EMGs were performed on abductor and adductor laryngeal muscles during respiratory cycles and spontaneous vocal fold abduction on day 4 and then weekly for 6 weeks. Vocal fold motion associated with spontaneous respiration was graded from 0 to 4. Rats were sacrificed at different time points for histologic evaluation of injured nerves. RESULTS: EMG signals showed fibrillation potentials on day 4 in all experimental conditions. Crushed RLN, regardless of force, exhibited polyphasic potentials at 2 weeks postinjury. Normal motor unit potentials and recruitment patterns were observed in EMG signals at 4 weeks for all 0.61 N clip animals. Six weeks following crush injury, motor unit potentials having normal appearance were observed in most animals. Synkinetic EMG signals were observed at 5 weeks and 6 weeks in the 1.19 N clip animals. Endoscopic evaluation of vocal fold mobility was consistently normal at 6 weeks only following 0.61 N crush injury. CONCLUSIONS: This model is useful to simulate intraoperative RLN injuries and to better understand the electrophysiologic events during nerve recovery. The severity of injury to the RLN dictates histologic, neurologic and functional recovery of the laryngeal motor system. This model is useful to evaluate the efficacy of systemic and local neurotropic agents in the treatment of RLN injury.

Evaluation of functional recovery of recurrent laryngeal nerve using transoral laryngeal bipolar electromyography: a rat model.

OBJECTIVES: We developed a standardized method of minimally invasive transoral laryngeal (ToL) bipolar electromyography (EMG) for evaluation of recurrent laryngeal nerve (RLN) recovery after a controlled crush injury in a rat model. METHODS: Ten 200- to 250-g Sprague-Dawley rats underwent a controlled crush injury to the left RLN performed with 60 seconds of use of a calibrated aneurysm clamp with a closing force of 0.61 N. Serial ToL bipolar EMG was performed on adductor muscles and the posterior criocoarytenoid muscle during spontaneous vocal fold motion under anesthesia. Each animal underwent ToL EMG immediately after surgery and 1, 3, and 6 weeks after surgery. RESULTS: The EMG signals showed normal motor unit potentials and recruitment patterns 3 weeks after crush injury. Endoscopic evaluation of vocal fold mobility yielded consistently normal findings 6 weeks after crush injury. CONCLUSIONS: We have developed a standardized method of crush injury to the rat RLN model and a minimally invasive transoral bipolar spontaneous EMG technique to serially evaluate and follow nerve injury and recovery in rats. This model is intended to simulate intraoperative RLN injury, to elucidate the electrophysiological events that occur during nerve recovery, and to form the basis for studying agents to enhance such recovery.

Ordered motor-unit firing behavior in acute cerebellar stroke.

It is known that at any given force level, the lower-threshold motor units generally fire at greater rates than the higher-threshold units during isometric tasks of extremity muscles. In addition to this hierarchical arrangement, firing rates of motor units fluctuate in unison with nearly no time delay; an observation that has led to the concept of common drive, a basic motoneuronal rule. Although it is established that the cerebellum plays a critical function in motor control, its role in the genesis, triggering, selection, and monitoring of motor-unit firing pattern discharges during isometric tasks is unknown. We applied an electromyographic (EMG) decomposition technique, known as precision decomposition, to accurately identify motor-unit firing times from the EMG signal recorded from the first dorsal interosseous muscle to unravel the features of motor-unit firings in three patients presenting a unilateral cerebellar stroke and exhibiting an acute cerebellar syndrome. We observed ataxic isometric force during visually guided abduction of the index finger on the affected side. However, the hierarchical response of individual motor units was spared. Furthermore, acute cerebellar ataxia was not associated with a loss of the common drive.

Assessing and documenting general competencies in otolaryngology resident training programs.

OBJECTIVES: The objectives of this study were to: 1) implement web-based instruments for assessing and documenting the general competencies of otolaryngology resident education, as outlined by the Accreditation Council of Graduate Medical Education (ACGME); and 2) examine the benefit and validity of this online system for measuring educational outcomes and for identifying insufficiencies in the training program as they occur. METHODS: We developed an online assessment system for a surgical postgraduate education program and examined its feasibility, usability, and validity. Evaluations of behaviors, skills, and attitudes of 26 residents were completed online by faculty, peers, and nonphysician professionals during a 3-year period. Analyses included calculation and evaluation of total average performance scores of each resident by different evaluators. Evaluations were also compared with American Board of Otolaryngology-administered in-service examination (ISE) scores for each resident. Convergent validity was examined statistically by comparing ratings among the different evaluator types. RESULTS: Questionnaires and software were found to be simple to use and efficient in collecting essential information. From July 2002 to June 2005, 1,336 evaluation forms were available for analysis. The average score assigned by faculty was 4.31, significantly lower than that by nonphysician professionals (4.66) and residents evaluating peers (4.63) (P < .001), whereas scores were similar between nonphysician professionals and resident peers. Average scores between faculty and nonphysician groups showed correlation in constructs of communication and relationship with patients, but not in those of professionalism and documentation. Correlation was observed in respect for patients but not in medical knowledge between faculty and resident peer groups. Resident ISE scores improved in the third year of the study and demonstrated high correlation with faculty perceptions of medical knowledge (r = 0.65, P = .007). CONCLUSIONS: Compliance for completion of forms was 97%. The system facilitated the educational management of our training program along multiple dimensions. The small perceptual differences among a highly selected group of residents have made the unambiguous validation of the system challenging. The instruments and approach warrant further study. Improvements are likely best achieved in broad consultation among other otolaryngology programs.

Frequency and voice: perspectives in the time domain.

SUMMARY: Frequency variation is one of the most primitive features of voice production, endowing language and communication with richness and efficiency and enhancing enjoyment of the voice arts. In the first of two tutorial articles, the subject of frequency is examined formally, beginning in the time domain. A companion article explores the topic of frequency and voice from the frequency domain perspective. Frequency is a well-defined quantity of the sinusoidal function and of periodic functions of time. However, voice is inherently nonstationary, even over short time segments, to degrees that range from minor (stable vowels of a healthy voice) to major (singing voice and voiced consonants). For signals that are not periodic, the notion of frequency is ambiguous and often altogether unclear, which has led to a multitude of frequency-measurement techniques and discrepancy of measures. This article identifies the source of these discrepancies for a variety of time-domain techniques that are examined in the absence of noise. In the time domain, the subject of frequency is inherently coupled to the topic of signal modeling, which is explored in some detail. Sinusoidal models having time-varying phase are examined with the objective of achieving a frequency description of voice that is both continuous and instantaneous. The analytic signal method of mathematical physics is discussed and applied to the technology of empirical mode decomposition to demonstrate that the frequencies of voice may be comprehensively examined from the time domain point of view.

The inspiratory maneuver: a simple method to assess the superficial lamina propria during endoscopy.

We describe a simple means of assessing the condition of the superficial lamina propria during endoscopy, which we use in our practice as an adjunct to careful stroboscopic examination. An intake of breath against partially adducted vocal folds serves to draw the mucosa inferomedially into the glottis, which reveals areas of diminished mobility, the relationship of mucosal lesions to deeper tissues of the vocal folds, and subtle submucosal lesions. This is possible because of the unique geometry of the glottis that renders the vector forces of airflow different at inspiration and expiration. Because the integrity of the superficial lamina propria is essential to healthy phonation, we have found the inspiratory maneuver useful across a wide variety of mucosal pathologic conditions.

Multiple motor unit recordings of laryngeal muscles: the technique of vector laryngeal electromyography.

OBJECTIVES: To display time-series firing rate and recruitment data for multiple, simultaneously active motoneurons activating human laryngeal muscles. These data provide specific information about how laryngeal muscle force is being controlled by the central nervous system at the level of the lower motoneuron. METHODS: A quadrifilar needle electrode was used to record multi-channel myoelectric signals from thyroarytenoid muscle of normal subjects during tasks ranging from quiet breathing to a short sentence. Motor unit action potentials of the signal space were identified and tracked throughout task productions using pattern recognition and Precision Decomposition software. RESULTS: We present the first recordings and analyses of multiple motor unit activations in the larynx. The firing times and mean firing rates are plotted for each identified motor unit, which reveal recruitment and decruitment information and the database from which common firing statistics across motor units may be derived. CONCLUSIONS: This study provides new information about neuromuscular physiology of the larynx. Specifically, the results reveal the ordered recruitment and firing patterns of multiple motor units and the existence of common drive from the central nervous system. The technique may prove fundamental to understanding various neuromuscular pathologies such as laryngeal spasm and to assist clinical prognosis of laryngeal paresis and the diagnosis of certain neurogenic disorders.