Abstract: This study investigated acoustic characteristics of American English liquids produced by native English (NE) and native Japanese (NJ) speakers reported in Aoyama, Flege, Guion, Akahane-Yamada, and Yamada [(2004). J. Phonetics 32, 233–250]. For a larger longitudinal study, the data were collected twice to investigate the acquisition of American English by the NJ speakers (Time 1, Time 2). Aoyama, Flege, Guion, Akahane-Yamada, and Yamada [(2004). J. Phonetics 32, 233–250] evaluated productions of /l/ and /ɹ/ in the NE and NJ adults and children (16 participants each) using NE speakers' perceptual judgments and showed that the NJ children's production of /ɹ/ improved from Time 1 to Time 2. In the current study, four acoustic parameters (duration, F1, F2, and F3) were measured in 256 tokens each of English /l/ and /ɹ/. Results showed that some acoustic parameters, such as F2, changed from Time 1 to Time 2 in the NJ speakers' productions, indicating improvements. However, the NJ speakers' productions were different from the NE speakers' productions in almost all acoustic parameters at both Time 1 and Time 2. Results suggest that the improvements in the NJ children's productions of /ɹ/ reported in Aoyama, Flege, Guion, Akahane-Yamada, and Yamada [(2004). J. Phonetics 32, 233–250] were due to a combination of changes, not due to a change in one acoustic parameter such as F3 in /ɹ/.
