Non-native talkers and listeners and the perceptual benefits of clear speech

This study examined the intelligibility benefit of native and non-native clear speech for native and non-native listeners when the first language background of non-native talkers and listeners is matched. All four combinations of talkers and listeners were tested: native talker-native listener, non-native talker-native listener, native talker-non-native listener, and non-native talker-non-native listener. Listeners were presented with structurally simple but semantically anomalous English sentences produced clearly or casually and mixed with speech-shaped noise at 0 dB signal-to-noise ratio and asked to write down what they heard. Results showed that native English speech was more intelligible than non-native speech and that native English listeners recovered speech better than non-native listeners did. Clear speech was significantly more intelligible than casual speech. There were no interactions between speaking style and native language background indicating that clear speech intelligibility benefit was not significantly different across distinct combinations of talkers and listeners. In particular, shared first language background among non-native speakers and listeners did not provide an extra benefit in either the overall speech intelligibility or the intelligibility gains of clear speech.