Accuracy of repetition of digitized and synthesized speech for young children in background noise

Purpose: The present study investigated the intelligibility of digitized and synthesized speech output in background noise for children 3-5 years old. The purpose of the study was to determine whether there was a difference in the intelligibility (ability to repeat) of 3 types of speech output (digitized, DECTalk synthesized, and MacinTalk synthesized) in single words and sentences, presented within and out of context. Method: The dependent variable was speech intelligibility (number of individual words repeated correctly). The study used a mixed-model design. Ninety typically developing children (3-5 years old) were assigned to each of 3 speech type conditions. Participants were asked to repeat 20 words and 10 short sentences. Half of the stimuli were preceded by contextual information (topic cue), and half were presented without any context. Results: Young children have difficulty accurately repeating some digitized and synthesized messages in background noise. Overall, the older children (4- and 5-year-olds) performed better than the 3-year-old children. Increasing information through context or longer messages (i.e., sentences) did facilitate intelligibility overall, although there was a statistically significant Message Length × Context × Speech Type interaction. Conclusions: For 3-5-year-olds, the intelligibility of single words is very low (55%-77%). The intelligibility of sentences is higher, but the sole use of sentences for communication is problematic. Contextual information facilitates intelligibility and is a promising approach for ensuring effective communication. Future research is needed to improve the intelligibility of speech output at the single word level in order to maximize the benefits of speech output.