Acoustic correlates of comorbid voice and resonance impairment in individuals with amyotrophic lateral sclerosis

Assessment of voice and resonance impairment in amyotrophic lateral sclerosis (ALS) may be challenging due to multi-speech subsystem involvement. Although several acoustic measures have been associated with isolated voice and resonance impairment, their efficacy in the presence of comorbid voice-resonance impairment is unclear. The goal of this work is to determine acoustic features that correlate with perceptual judgment of voice and resonance severity in patients with ALS, and identify measures capable of differentiating phonatory, resonance, and co-occurring impairments. Two listeners rated resonance and voice impairment severity of repetitions of “Buy Bobby a puppy” produced by 26 participants with ALS. Samples were stratified based on perceptual ratings: bulbar asymptomatic, predominantly phonatory involvement (i.e., abnormal voice), predominantly resonatory involvement (hypernasality), and mixed (phonatory and resonance involvement). Groups were compared using resonance (one-third octave analysis) and phonatory (cepstral/spectral) measures. The one-third octave analysis differentiated all groups (p < 0.05); the cepstral peak prominence differentiated all groups (p < 0.01) except asymptomatic versus mixed; and the low/high spectral ratio did not differ between groups. Findings illustrate the challenges of implementing targeted resonance and voice measures in the presence of multi-speech system involvement, though one-third octave analysis is a promising approach to quantifying voice and resonance impairment in ALS.