The effect of speech compression on second language speech perception learning
Takahiro Adachi, Tsuneo Yamada · The Journal of the Acoustical Society of America · 2002
In recent years, second language education is sometimes conducted over the Internet. However, the speech used for training is often compressed in order to decrease the number of packets transmitted, without an evaluation of whether the compression causes a decrease in intelligibility. The current study assessed the intelligibility of compressed speech in order to determine whether it is appropriate for use in Internet-based training. English words minimally contrasting in /r/ and /l/, /b/ and /v/, or /s/ and /th/ were recorded from native speakers of English and compressed using several different methods (MP3, WMA, QCELP, ADPCM, etc.). The intelligibility of these speech files was then evaluated by a group of native English speakers and a group of native Japanese speakers, using a minimal-pair identification task. Results showed that: (1) intelligibility scores for Japanese speakers were lower than those for the English speakers, as was expected; and (2) intelligibility of /r/–/l/ stimuli was unaltered by the compression, whereas intelligibility of /s/–/th/ stimuli dropped remarkably in several formats, and that of /b/–/v/ stimuli dropped only in QCELP-compressed words. These findings suggest that some compression formats are not appropriate in speech perception training. Implications for Internet educational materials will be discussed.