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 factors personal factors

participation

health condition

e.g. dysarthria

Index of severity

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

speakermessage

transmission system listener

targetinfluencing

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

1 .op ø b d f g h j k l m n p r s t v w z

1. dop

2. nuis

3.

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 dimensionse.g.: voice, place of articulation, manner of articulation, …

if these features are able to predict intelligibilitygood chance they can characterize the articulation of a pathological speaker

Thank you!