Relationship Between Speech Intelligibility and Speech Comprehension in Babble Noise
Résumé
Purpose: The authors investigated the relationship between the intelligibility and comprehension of speech presented in babble noise. Method: Forty participants listened to French imperative sentences (commands for moving objects) in a multi-talker babble background for which intensity was experimentally controlled. Participants were instructed to transcribe what they heard and obey the commands in an interactive environment set up for this purpose. The former test provided intelligibility scores and the latter provided comprehension ones. Results: Collected data reveal a globally weak correlation between intelligibility and comprehension scores (r = .35, p < .001). The discrepancy tends to grow as a function of noise level increase. An analysis of standard deviations shows that variability in comprehension scores increases linearly with noise level whereas higher variability in intelligibility scores is found for moderate noise level conditions. Conclusion: These results support the hypothesis that intelligibility scores are poor predictors of listeners' comprehension in real communication situations. Intelligibility and comprehension scores appear to provide different insights, the first measure being centered on speech signal transfer and the second on communicative performance. Both theoretical and practical implications for the use of speech intelligibility tests as indicators of speakers' performances are discussed.