Comparison of thumb-pressure vs. electromyographic modes of frequency modulation for electrolaryngeal speech

Abstract

Speaking with natural prosodic patterns is tremendously challenging when using an electrolarynx (EL). Some ELs enable dynamic fundamental frequency (f0) variation to provide prosodic patterns and thereby improve speech naturalness. This study compares EL speech produced using thumb-pressure f0 variation (TruTone™ EL) versus an experimental method wherein f0 variation is derived from submental (under chin) electromyographic (EMG) signals (EMG-EL). Eighteen Laryngectomees provided sentence-length samples of speech using these two EL devices, and measures of f0 mean, SD and range were made. The f0 coefficient of variation (f0CV; SD f0/mean f0) was also calculated as a measure of f0 variation relative to the mean (Cartei et al., 2012). Paired t-tests of f0 measures were used to compare EL devices within participants. Mean f0 range was significantly greater for the EMG-EL device than thumb-pressure EL device (16 of 18 speakers; p <.05). Although mean f0 was roughly the same across devices, f0CV was significantly higher for the EMG-EL than thumb-button EL (17 of 18 speakers; p<.05). The EMG-EL device enabled greater f0 variation than a thumb-pressure-controlled device, which is consistent with our prior findings that the EMG-EL supports more natural-sounding speech—even for EL users who own the thumb-pressure device.