HSC Section 6 Nov2016 Green Book

Annals of Otology, Rhinology & Laryngology 123(4)

Table 1.  Means for Intensity Level at 65 dB. Variable

intensity targets (65 and 75 dB [± 3 dB]). These intensity targets were chosen to represent a typical healthy vocaliza- tion intensity range present in everyday speech. In this con- dition, participants received visual feedback of their intensity level by monitoring a dB sound level meter placed 16 inches from the individual’s mouth. The participant was asked to hold the intensity constant for a minimum of 3 sec- onds. Trials less than 3 seconds were not accepted for analy- sis. A total of 10 trials of each task condition were recorded. The initial and final 2 trials were discarded, leaving 6 trials for post-hoc data analysis. Habitual fundamental frequency (F o ) for the vocalization tasks was initiated by the participant without prompting from the investigators. The F o chosen by the participant was recorded and played back via an auto-tuner before data col- lection so that the participant could remain in an acceptable modal pitch range. Before all data collection procedures and to ensure performance consistency, each participant was trained and given time to practice all tasks before data collection. Data Analysis A 2-factor repeated measures analysis of variance (RM-ANOVA) was used to compare the effect of the 2 independent variables among participants. The independent variables included (1) LEMG data recording sessions (3 sessions) and (2) the task-related vocal intensity levels (2 dB levels). To evaluate the reliability of LEMG signals across testing times, intraclass correlation coefficients (ICCs) using a 2-way mixed random effects model were calculated. For between-session measurements, standard error of the measurement (SEM) was calculated to deter- mine the minimum detectable change (MDC) in microvolts with 70% and 95% confidence boundaries. Intraclass cor- relations were also calculated to measure intra-session reli- ability. All statistical calculations were performed using SPSS version 18 (IBM, Armonk, New York, USA). Data Selection and Calculations A 1-second window from the mid-portion of each 3-second task recording window was selected for detailed analysis. Root mean square amplitude values were automatically calculated for each of the 1-second windows using a cus- tom sub-routine in LabChart (ADInstruments, Inc). To be included for further processing and analysis, digitized sam- ples had to fall within +/– 1 dB of the desired intensity levels (65 or 75 dB). In certain cases, the RMS amplitude was not stable for 1 second at +/– 1 dB. In these cases, a shorter window was averaged to eliminate portions of the signal with poor signal quality. The inclusion of smaller analysis windows for these cases was preferable to averag- ing poor signal quality. Smaller sampling windows do not

Session Mean SD Min Max

Root mean square (µV) 

1 80.2 34.8 44.7 151.5 2 91.8 28.4 45.4 117.6 3 73.08 19.64 46.31 98.48

Table 2.  Means for Intensity Level at 75 dB. Variable

Session Mean SD Min Max

Root mean square (µV)

1 84.0 37.4 46.0 155.5 2 106.5 29.4 69.2 136.9 3 85.04 16.82 55.42 101.56

Table 3.  Repeated Measures Analysis of Variance for Baseline Laryngeal Electromyography Across Time. Source df F Value P Value Participant 6 0.85 .555 Time 2 0.02 .978 Table 4.  Repeated Measures Analysis of Variance for Root Mean Square Values. Source df F Value P Value Participant 6 1.91 .160 Time 2 1.38 .289 Intensity 1 5.71 .054 Time*Intensity 2 2.23 .150

significantly affect analyses, as comparisons of EMG sam- ple windows using RMS have been shown to produce mod- erate to excellent ICC reliability data from 1000 ms down to 100 ms window sizes. 13

Results Statistical Analysis

Group data, including means and standard deviations for the dependent variable (RMS) for intensities at 65 dB and 75 dB, are presented in Tables 1 and 2, respectively. Results of the 2-factor RM-ANOVA during baseline and the task conditions are presented in Tables 3 and 4. Repeated mea- sures ANOVA for the baseline data did not reveal a signifi- cant main or interaction effect for testing time (session) versus RMS, indicating stable LEMG baseline activity across recording sessions. Results of the RM-ANOVA for the feedback condition were not significant for the main effect of testing time ( df = 2, F = 1.38, P = .289). However, the main effect for intensity level closely approached our a

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