Conversational and clear speech intelligibility of /bVd/ syllables produced by native and non-native English speakers

Abstract

The ability of native and non-native speakers to enhance intelligibility of target vowels by speaking clearly was compared across three talker groups: monolingual English speakers and native Spanish speakers with either an earlier or a later age of immersion in an English-speaking environment. Talkers produced the target syllables "bead, bid, bayed, bed, bad" and "bod" in 'conversational' and clear speech styles. The stimuli were presented to native English-speaking listeners in multi-talker babble with signal-to-noise ratios of Ϫ8 dB for the monolingual and early learners and Ϫ4 dB for the later learners. The monolinguals and early learners of English showed a similar average clear speech benefit, and the early learners showed equal or greater intelligibility than monolinguals for most target vowels. The 4-dB difference in signal-to-noise ratio yielded approximately equal average intelligibility for the monolinguals and later learners. The average clear speech benefit was smallest for the later learners, and a significant clear speech decrement was obtained for the target syllable "bid." These results suggest that later learners of English as a second language may be less able than monolinguals to accommodate listeners in noisy environments, due to a reduced ability to improve intelligibility by speaking more clearly.

Bidirectional clear speech perception benefit for native and high-proficiency non-native talkers and listeners: Intelligibility and accentedness

“…Clear speech strategies of more fluent non-native talkers, therefore, can be as beneficial for the native listeners as those of native talkers. Rogers et al (2010) found a similar pattern of increased intelligibility of CVC syllables for the early learners compared to the late learners of English. Interestingly, the non-native talkers and listeners in the present study are not simultaneous or even early bilinguals.…”

“…Note that the type of the materials, noise, listeners and talker characteristics are all going to affect the level of noise acceptable to achieve similar baseline performance (cf. Rogers et al, 2010). The intelligibility results for the matched native listeners and native talkers reported in Smiljanić and Bradlow (2005) and pilot testing were used as a baseline in deciding the noise levels in the experiments reported here.…”

“…They found a substantially smaller clear speech gain for non-native listeners compared to native listeners. In a recent investigation of the ability of non-native talkers to enhance intelligibility of vowels in bVd syllables for native English listeners, Rogers et al (2010) found that monolingual English speakers and early learners of English provided a similar and large clear speech benefit compared to the late learners of English who produced the smallest clear speech gain for native English listeners (background L1of both non-native groups was Spanish). The late learners, those who had least experience with the target English sounds, even exhibited a decrease in clear speech intelligibility for the vowel/I/in "bid."…”

“…Due to their inexperience, low proficiency non-native talkers may fail to enhance some of the acoustic-phonetic features typically produced in L2 clear speech which may result in a smaller intelligibility advantage for native listeners (cf. early bilinguals in Rogers et al, 2010). Similarly, non-native listeners may not perceive and utilize subtle acoustic-phonetic cue enhancements specific to L2 and may therefore benefit less from L2 clear speech compared to native listeners (cf.…”

“…Clear speech production and perception should become more in line with native clear speech processing with increased exposure to the target language (cf. late vs early learners of English in Rogers et al, 2010).…”