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Assessing Speech Intelligibility and Severity

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

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

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

4 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)

5 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

6 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

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

10 Comparison of PCC and PDS Severity Ratings
Mild >90% Mild-Mod 65-85% Mod-Sev 50-65% Severe <50% PDS Mild pts Moderate 20-39 Severe 40-59 Profound 60+

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)
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

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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