Intelligibility: effects of transcription analysis and speech stimulus.

Background: intelligibility measures are limited to providing information on the severity level of clinical cases. A key limitation is that such measures are sensitive to changes in performance only in subjects with a determined severity level of speech disturbance.

Aim: to investigate the influence of stimuli type and transcription analysis on intelligibility measures of speakers with no communication disorders.

Method: an experimental study with no intervention procedures was developed. Two groups of subjects with no communication disorders took part in the research. The group of speakers was composed by 30 adults. Speech samples were recorded by repeating three lists of stimuli (sentences, words and non-words) equally distributed according to parameters of frequency of phonemes, syllabic structures and word length. The group of listeners was composed by 60 young adults who orthographically transcribed the speech samples. Two transcription intelligibility measures were obtained for each list of stimuli: percentage of correct answers per syllable unit and per item (for each sentence, word and non-word).

Results: intelligibility scores were statistically higher for syllable units than for the other items. Regarding intelligibility scores per syllables, a statistical difference was observed amongst scores for sentences, words and non-words.

Conclusion: both transcription analysis and stimulus type influenced the intelligibility scores of the studied population, especially when non-words were used as speech material. The handling of these variables can help to improve intelligibility tests.