Differences in intelligibility of non-native directed speech and hearing impaired directed speech for non-native listeners

Within the field of clear speech research, non-native, hearing impaired, and child-directed speech are often referred to as types of 'clear speech.' However, although some research has compared the acoustic properties of these types of speech, no research has directly compared their intelligibility. In the present study, non-native listeners completed a sentence transcription task for non-native and hearing impaired directed speech. Results showed no significant difference in performance between the two speaking conditions, indicating that the phonological adjustments talkers make when addressing non-native versus hearing impaired listeners do not have any significantly different effect on intelligibility.