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Why an objective intelligibility assessment ?. Gwen Van Nuffelen Marc De Bodt. Catherine Middag Jean-Pierre Martens. Speech intelligibility. The degree to which a listener understands the auditory signal produced by a speaker Duffy 2007
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Why an objective intelligibility assessment ? Gwen Van Nuffelen Marc De Bodt Catherine Middag Jean-Pierre Martens
Speech intelligibility • The degree to which a listener understands the auditory signal produced by a speaker • Duffy 2007 • Different linguistic levels: phoneme – word – sentence – connected speech • Clinical relevance? • Model of Functioning, Disability and Health (WHO, 2001)
health condition e.g. dysarthria body functions and structures phonatory, articulatory, resonatory and respiratory muscles activity speech intelligibility participation Index of severity environmental factors personal factors
Golden standard • Perceptual intelligibility assessments • Scaling: rough overall index • Measurements (%): more accurate index, procedures and test materials can be standardized Important for reliability and validity
Reliability and validity speaker message transmission system listener influencing factors target
Reliability and validity • transmission system: easy to control / standardize • listener: intelligibility score depends upon the listener’s • familiarity with speaker/ speaker’s accent/ cultural background/ pathology • familiarity with test items • test items: predictability • solutions
Reliability and validity large pool of test items & random selection e.g. Assessment of Intelligibility of Dysarthric Speech (Yorkston, 1981) non-existing words syntactically correct sentences conveying no meaningful message e.g. Swedish Intelligibility Test (Lillvik, 1999) Artificial Negative effect on naturalness Dutch adult patients: Dutch Intelligibility Assessment (De Bodt et al. 2006)
DIA • Intelligibility at phoneme level • 50 consonant – vowel – consonant words • 3 subtests: • A: initial consonants (19 words) • B: final consonants (15 words) • C: medial vowels/ diphthongs (16 words) • Measures to improve reliability • Balanced mix of existing and non-existing (well pronounceable) words • Large pool of test items: 25 lists of words / subtest • Random selection • In each list: one randomly selected phoneme occurs twice
top DIA List A10
Reliability and validity • Advantage of a speech technology based intelligibility assessment • Computer replaces human listener • No need for a large pool of test items and random selection • No need for artificial features needed
Space intelligibility tool • acoustic models of phonemes phonemic features • and/or • acoustic models of phonemes phonological features articulatory dimensions e.g.: voice, place of articulation, manner of articulation, … if these features are able to predict intelligibility good chance they can characterize the articulation of a pathological speaker