Effects of discourse context on the intelligibility of synthesized speech for young adult and older adult listeners: Applications for AAC

The use of speech synthesis in electronic communication aids allows individuals who use augmentative and alternative communication (AAC) devices to communicate with a variety of partners. However, communication will only be effective if the speech signal is readily understood by the listener. The intelligibility of synthesized speech is influenced by a variety of factors, including the provision of context. Although the facilitative effects of context have been demonstrated extensively in studies with young adults, there are few investigations into older adults' ability to decode the synthesized speech signal. The present study investigated whether discourse context affected the intelligibility of synthesized sentences for young adult and older adult listeners. Listeners were asked to repeat 15-word sentences that were either presented in isolation or preceded by a story that set the context for the sentence. Participants correctly repeated significantly more words in the sentences when they were preceded by related sentences than when the sentences were presented in isolation. This research shows a facilitating effect of context in discourse, wherein previous words and sentences are related to later sentences, for both younger and older adult listeners. These results have direct implications for AAC system message transmission.