Assessing Speech Intelligibility and Severity

Assessing Speech Intelligibility and Severity What are some standard procedures? Are measures of intelligibility and severity the same? Although judgements about intelligibility and severity may be correlated, they represent two

different indices about an individuals speech For example, a child may have a severe resonance disorder, but his/ her speech is still intelligible Intelligibility Scales

Typically a panel of 2-5 listeners (expert ~ novice; familiar ~ unfamiliar) rate a taped (audio or video) segment of childs speech Rank intelligibility of childs speech compared to age peers Scales typically use 3-point or 5point judgment scales (See Bleile) scores are averaged to derive a composite intelligibility rating score Intelligibility Scales

Kent, Miolo, & Bloedel (1994) compared 19 intelligibility measures according to 5 categories that differed with regard to the emphasis of the analysis (phonetic ~ phonemic; word level ~ conversation) Intelligibility Scales Listed 8 factors that influence clinical evaluation of intelligibility:

loss of phonological contrasts loss of contrasts in specific environments extent of homonymy amt of difference between target~realization frequency of occurrence in English

consistency familiarity of listener with speaker context in which communication occurs Intelligibility Weston & Shriberg (1992) concluded that articulation variables alone cannot account for all the breakdowns that result in communication other general contextual and linguistic variables are related to

speech intelligibility Severity Similar to intelligibility rating scales, a panel of familiar or unfamiliar listeners judge a segment of a childs recorded (audio or video-taped) speech (single word or connected speech) Severity

Perceptual scales (see Bleile) or quantitative measures 4 Point Clinical Judgement Scale of Severity No disorder-Mild-Moderate-Severe average score of 3.5 often required to provide clinical services Severity Quantitative Measures PCC (and 8 variations)

Hodsons PDS Edwards PDI Comparison of PCC and PDS Severity Ratings PCC PDS Mild >90% Mild

1-19 pts Mild-Mod 65-85% Moderate 20-39 Mod-Sev 50-65% Severe

40-59 Severe <50% Profound 60+ Shriberg, Austin, Lewis, McSweeny, & Wilson (1997) 9 speech metrics

PCC (based on conv speech) PCC-A (common clinical distortions scored correct) PCC-R ([un]common distortion scored correct) ACI (differentially weighs distortion ~ sub/omis) PCI (percentage of sounds mastered-early talkers) PVC (similar to PCC, but for vowels/diphthongs) PVC-R (similar to PCC-R, but for vowels/diphthongs) PPC (percentage to consonants/vowels correct) PPC-R (scores distortions correct) Which metric is most appropriate? Depends on specific needs of the assessment Interest limited to consonants

PCC, PCC-A, PCC-R, ACI Young/severely delayed children PCI Interest in vowels/diphthongs PVC, PVC-R Interest in articulation competence on all speech sounds PPC, PPC-R Rafaat, Rvachew, & Russell (1995)

Purpose of study was to determine the percentage of agreement between SLPs in rating PI severity Adequate reliability for older children (4;6+), but unreliable for children under 3;6 Unable to reliably distinguish TD from mild delay Why were SLPs less reliable on severity

ratings of younger children? What factors account for differences in reliability ratings?