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Assessing Speech Intelligibility and Severity What are some standard procedures?

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1 Assessing Speech Intelligibility and Severity What are some standard procedures?

2 Are measures of intelligibility and severity the same? l Although judgements about intelligibility and severity may be correlated, they represent two different indices about an individual’s speech l For example, a child may have a severe resonance disorder, but his/her speech is still intelligible

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

4 Intelligibility Scales l 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)

5 Intelligibility Scales l 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

6 Intelligibility l 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

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

8 Severity l 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

9 Severity l Quantitative Measures PCC (and 8 variations) Hodson’s PDS Edwards’ PDI

10 Comparison of PCC and PDS Severity Ratings PCC Mild>90% Mild-Mod65-85% Mod-Sev50-65% Severe<50% PDS Mild1-19 pts Moderate20-39 Severe40-59 Profound60+

11 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)

12 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

13 Rafaat, Rvachew, & Russell (1995) l Purpose of study was to determine the percentage of agreement between SLPs in rating PI severity l Adequate reliability for older children (4;6+), but unreliable for children under 3;6 l Unable to reliably distinguish TD from mild delay

14 Why were SLPs less reliable on severity ratings of younger children?

15 What factors account for differences in reliability ratings?


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