Rate and Loudness Manipulations in Dysarthria

Abstract

Both rate reduction and increased loudness reportedly are associated with an increase in the size of the articulatory-acoustic working space and improved acoustic distinctiveness for speakers with dysarthria. Improved intelligibility also has been reported. Few studies have directly compared rate and loudness effects for speakers with dysarthria, however, although rate reduction and increasing vocal loudness are common treatment techniques. In the current study, 15 speakers with dysarthria secondary to multiple sclerosis, 12 speakers with dysarthria secondary to Parkinson's disease (PD), and 15 healthy controls read a passage in habitual, loud, and slow conditions. Rate and loudness variations were elicited using magnitude production. Acoustic measures included articulatory rate, sound pressure level, vowel space area, first moment difference measures, and F2 trajectory characteristics for diphthongs. Ten listeners scaled intelligibility for reading passages produced by the speakers with dysarthria. Relationships between intelligibility estimates and acoustic measures were determined by regression analysis. All speaker groups reduced articulatory rate for the slow condition and increased vocal intensity for the loud condition, relative to the habitual condition. Vowel acoustic distinctiveness, as indexed by vowel space area, was maximized in the slow condition, but stop consonant acoustic distinctiveness, as indexed by first moment difference measures, was maximized in the loud condition. F2 slope measures for diphthongs were not consistently affected by rate or loudness. Scaled intelligibility for speakers with PD also improved in the loud condition relative to both the habitual and slow conditions. Intelligibility estimates for speakers with dysarthria, however, were not strongly related to acoustic measures of supraglottal behavior. Findings are compared with previous studies, and hypotheses for future treatment studies are discussed.

Clear Speech Variants: An Acoustic Study in Parkinson's Disease

“…Some studies have also reported reduced sound pressure levels (SPLs; Fox & Ramig, 1997;Skodda, Visser, & Schlegel, 2011b;Tjaden et al, 2013;Walsh & Smith, 2011). However, other studies have reported no differences in mean SPL for speakers with PD relative to healthy controls (Canter, 1963;Sadagopan & Huber, 2007;Tjaden & Wilding, 2004). Last, a variety of studies have reported rate abnormalities in PD (Canter, 1963(Canter, , 1965Flint et al, 1992;Hammen & Yorkston, 1996;Ludlow & Bassich, 1983;Metter & Hanson, 1986;Solomon & Hixon, 1993;Skodda & Schlegel, 2008), although other studies reported no differences in rate relative to healthy controls (Ackermann & Ziegler, 1991;Caligiuri, 1989;Goberman et al, 2002).…”

“…Acoustic variables likely explaining these intelligibility variations are suggested in a variety of studies. For example, segmental metrics such as static and dynamic vowel measures, consonant spectral moments, and consonant distinctiveness measures have been reported as predictors of intelligibility (Amano-Kusumoto, Holsom, Kain, & Aronoff, 2014;Fogerty, 2013;Fogerty & Humes, 2010;Kay, 2012;Kim et al, 2011;Lansford & Liss, 2014;Maniwa, Jongman, & Wade, 2008;Owren & Cardillo, 2006;Tjaden & Wilding, 2004;Turner et al, 1995;Weismer, Martin, Kent, & Kent, 1992). In addition, suprasegmental measures of F0 and global timing measures have shown to be strong predictors of intelligibility (Bradlow, Torretta, & Pisoni, 1996;Bunton, Kent, Kent, & Duffy, 2001;Kim et al, 2011;Laures & Weismer, 1999).…”

“…More recent acoustic studies have helped characterize the nature of the speech impairment in PD. For example, relative to healthy controls, speakers with PD produce more centralized vowel space areas (VSAs; Liu, Tsao, & Kuhl, 2005;Tjaden, Lam, & Wilding, 2013;Turner, Tjaden, & Weismer, 1995;Weismer, Jeng, Laures, Kent, & Kent, 2001), less spectrally distinct consonants (Tjaden & Wilding, 2004), weakened or less precise stop closures (Ackermann & Ziegler, 1991), and shallower second formant (F2) slopes, indicating slowed changes in vocal tract adjustments (Kent & Adams, 1989;Kim, Kent, & Weismer, 2011;Walsh & Smith, 2011). At the suprasegmental level, speakers with PD tend to pause more often (Torp & Hammen, 2000; but see Goberman & Elmer, 2005), utilize an increased fundamental frequency (F0; Canter, 1963;Goberman, Coelho, & Robb, 2002), and exhibit decreased variability in F0 (Canter, 1963(Canter, , 1965Flint, Black, Campbell-Taylor, Gailey, & Levinton, 1992;Skodda, Visser, & Schlegel, 2011a).…”

“…Stop onsets were defined as the left edge of the first stop burst release, and offsets were defined as the point where aspiration intensity reached a minimum prior to the onset of vowel periodicity. For stops, M1 coefficients were obtained for a 20-ms interval starting at the left edge of the release burst (Tjaden & Wilding, 2004). For every speaker, condition, and stop consonant (t, k), the mean of M1 was averaged across productions.…”

Listener Perception of Monopitch, Naturalness, and Intelligibility for Speakers With Parkinson's Disease

“…The first author heard the speech stimuli multiple times to ensure that the chosen monologue samples were representative of the speaker's natural speech pattern. The selected speech stimuli were edited to be of approximately 2 s each in Audacity software (version 2.0.5), and each utterance consisted of one to two complete sentences, similar to previous studies (Nagle & Eadie, 2012;Spielman, Ramig, Mahler, Halpern, & Gavin, 2007;Tjaden & Wilding, 2004;Weismer & Laures, 2002). All stimuli were amplitude normalized, and speech-shaped noise was added for judgments of intelligibility.…”