Clear speech is a speaking style adopted by speakers in an attempt to maximize the clarity of their speech and is proven to be more intelligible than casual speech. This work focuses on modifying casual speech to sound as intelligible as clear speech. To that purpose, a database of read speech sentences, recorded both in clear and in casual speaking style is analyzed. Based on the analysis of the database, speaking rate is the prevalent characteristic that differs between the two speaking styles. To examine if speaking rate plays role in the intelligibility advantage of clear speech, clear speech signals are time scaled in higher speaking rate to match the duration of the casual signals. Subjective and objective measures on time-scaled clear speech and casual speech, revealed that the low speaking rate is the main factor that contributes to clear speech intelligibility. However, when attempting to expand casual signals in time, the intelligibility of the casual signals deteriorates. Since time scale modifications on casual signals seem inappropriate of increasing intelligibility, spectral transformations on the casual speech signals are performed. Subjective and objective tests show a significant enhancement of the intelligibility of casual signals, reaching the intelligibility scores of clear signals.
Index Terms: Clear speech, Casual speech, Speech intelligibility, Spectral modifications
Bibliographic reference. Koutsogiannaki, Maria / Pettinato, Michelle / Mayo, Cassie / Kandia, Varvara / Stylianou, Yannis (2012): "Can modified casual speech reach the intelligibility of clear speech?", In INTERSPEECH-2012, 579-582.