Comparing Neurologic Disorders by Voice Modulation Profiles

E Buder, E Strand, L Hartelius, M Cannito, L Chorna, S Bansberg, C Adler

Many neurologic disorders are known to impair individuals’ abilities to maintain long-term stable phonation, but the resulting phonatory instabilities may occur in a variety of forms. The modulogram technique assesses and quantifies types of phonatory instability under a common framework to encompass both f₀ and SPL as acoustic parameters, and also across the separate frequency domains of wow, tremor, and flutter. The technique makes possible more direct comparisons between neurologic groups. The neurological disorders studied here (including amyotrophic lateral sclerosis, multiple sclerosis, adductor spasmodic dysphonia, and essential tremor) can, through modulographic analysis, be more or less distinctly characterized by profiles of vocal modulation types. The work reported here also compares such profiles to age-specific baseline modulations of neurologically normal individuals. It is anticipated that these profiles will ultimately help with basic understanding of neurological mechanisms governing voice stability and the various ways such mechanisms may fail.