Direct Magnitude Estimates of Speech Intelligibility in Dysarthria

Abstract

Direct magnitude estimation (DME) has been used frequently as a perceptual scaling technique in studies of the speech intelligibility of persons with speech disorders. The technique is typically used with a standard, or reference stimulus, chosen as a good exemplar of "midrange" intelligibility. In several published studies, the standard has been chosen subjectively, usually on the basis of the expertise of the investigators. The current experiment demonstrates that a fixed set of sentence-level utterances, obtained from 4 individuals with dysarthria (2 with Parkinson disease, 2 with traumatic brain injury) as well as 3 neurologically normal speakers, is scaled differently depending on the identity of the standard. Four different standards were used in the main experiment, three of which were judged qualitatively in two independent evaluations to be good exemplars of midrange intelligibility. Acoustic analyses did not reveal obvious differences between these four standards but suggested that the standard with the worst-scaled intelligibility had much poorer voice source characteristics compared to the other three standards. Results are discussed in terms of possible standardization of midrange intelligibility exemplars for DME experiments.

Estimating the Intelligibility of Speakers with Dysarthria

“…These measures generally require listeners to quantify their qualitative judgments of a speaker's intelligibility by assigning a number to what they heard. Variations on this method include use of equal-appearing interval scales [2,[8][9][10] , direct magnitude estimation (DME) [10][11][12][13][14] , and percent estimates [4,15] . One of these subjective measures, percent estimates, was of interest for the present study.…”

Effect of Level of Presentation to Listeners on Scaled Speech Intelligibility of Speakers with Dysarthria

“…Modifications of speech signal intensity, simply via amplification or attenuation, do not change articulation and therefore may permit an independent estimate of the relationship between signal intensity and intelligibility, as in the Neel [18] study. Moreover, it would be useful to have such data for scaled estimates of speech intelligibility, which are used frequently in studies of dysarthria [19,20] and in popular clinical exams that may also be used in research studies (such as the UPDRS [21] and Frenchay [22,23] ). The purpose of the present study was to explore the effects of the (1) presentation level and (2) across-sentence equalization of speech-signal intensities on direct magnitude estimates (DME) of speech intelligibility of sentences produced by persons with dysarthria and control speakers.…”

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.…”