Why an objective intelligibility assessment ? Catherine Middag Jean-Pierre Martens Gwen Van Nuffelen Marc De Bodt

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)

body functions and structures phonatory, articulatory, resonatory and respiratory muscles activity speech intelligibility environmental factorspersonal factors participation health condition e.g. dysarthria Index of severity

Clinical relevance 1.depends upon the main subsystems of speech articulation resonance phonation prosody / respiration 2. an index of severity of functional limitations to document the disorder therapy outcome measure monitoring change in performance over time 3. gives an idea of adequacy of communication & the impact on participation in daily life

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 target influencing factors

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

DIA top 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

Thank you!