Abstract
Background and Purpose The aim of the study was to compare transcription-based speech intelligibility and
scaled speech severity for the detection of mild speech impairments, by studying these
metrics across talkers with Parkinson's disease (PD), age- and sex-matched older adults,
and younger adults. An additional aim was to determine the impact of listener experience
on these clinical measures.
Methods Fifteen speakers from each experimental group were asked to read aloud 11 randomly
generated sentences from the Speech Intelligibility Test at their typical speaking
rate and loudness. Two groups of four listeners each, stratified as experienced or
inexperienced listeners based on their clinical experience, judged the sentence samples.
To estimate intelligibility, both listener groups were asked to orthographically transcribe
exactly what they heard for each sentence. For severity estimates, the listener groups
were asked to rate the sentences for overall quality based on voice, resonance, articulation,
and prosody, using a visual analog scale.
Results Transcription-based intelligibility and scaled severity scores of the PD group differed
significantly from those of the older and younger adults. Between-age group differences
in intelligibility and scaled severity were not observed. Listener experience had
an impact on scaled speech severity, but not speech intelligibility. Between-group
differences in speech severity were driven by the inexperienced group and not the
experienced listener group.
Implications Both transcription-based intelligibility and scaled severity estimates appear to
be sensitive to relatively mild speech impairments in PD. Obtaining scaled severity
is less labor intensive than transcription; therefore, visual analog scaling may be
the preferred paradigm for clinical use. However, listener experience and training
are important considerations for scaling techniques to be implemented clinically.
Keywords
Parkinson's disease - dysarthria - speech intelligibility - speech severity - visual
analog scale
