This study aimed to investigate English sentence recognition in quiet and two types of maskers, multi-talker babble (MTB) and long-term speech-shaped noise (LTSSN), with varied signal-to-noise ratios, for English-, Chinese-, and Korean-native listeners. Results showed that first, sentence recognition for non-native listeners was affected more by background noise than that for native listeners; second, the masking effects of LTSSN were similar between Chinese and Korean listeners, but the masking effects of MTB were greater for Chinese than for Korean listeners, suggesting possible interaction effects between the non-native listener's native language and speech-like competing noise in sentence recognition.

Regardless of differences in hearing status, the degree and pattern of aging effect on auditory processing of the NH listener groups were similar to those of the CI listener groups. This result suggests that age-related declines in speech understanding are likely multifactorial, including peripheral and central factors. Although the age cutoff of the current older age group was 10 yr less than in previous studies (Dubno et al, 2002; Lin et al, 2011), we still found the age-related differences on two auditory tasks. This study extends the knowledge of age-related auditory perception difficulties to CI listeners.

The identification of 12 English vowels was measured in quiet and in long-term speech-shaped noise (LTSSN) and multi-talker babble for English-native (EN) listeners and Chinese-native listeners in the U.S. (CNU) and China (CNC). The signal-to-noise ratio was manipulated from -15 to 0 dB. As expected, EN listeners performed significantly better in quiet and noisy conditions than CNU and CNC listeners. Vowel identification in LTSSN was similar between CNU and CNC listeners; however, performance in babble was significantly better for CNU listeners than for CNC listeners, indicating that exposing non-native listeners to native English may reduce informational masking of multi-talker babble.

The current study examined Vowel Inherent Spectral Change (VISC) of English vowels spoken by English-, Chinese-, and Korean-native speakers. Two metrics, spectral distance (amount of spectral shift) and spectral angle (direction of spectral shift) of formant movement from the onset to the offset, were measured for 12 English monophthongs produced in a /hvd/ context. While Chinese speakers showed significantly greater spectral distances of vowels than English and Korean speakers, there was no significant speakers' native language effect on spectral angles. Comparisons to their native vowels for Chinese and Korean speakers suggest that VISC might be affected by language-specific phonological structure.

Sixteen American-English vowels including 12 monothongs and 4 diphthongs were recorded in a phonetic context of /hVd/ from young English (E), Chinese (C), and Korean (K) talkers. The Chinese and Korean talkers were bilingual and had stayed in United States up to 6 years. Two sets of experiments will be discussed: acoustic analysis and intelligibility of English vowels produced by the three groups of talkers. Results of acoustic analysis showed that there was no significant difference in F1×F2 vowel space among the three groups of talkers. In addition, the three groups of talkers showed great similarity in F2/F1 ratio across the 12 monothongs. Vowel durations had significantly greater variability across vowel categories for the Chinese and Korean talkers than for the English talkers, indicating that, besides producing spectral differences among vowels, Chinese and Korean talkers also attempted to generate durational difference among vowels to make each vowel distinguishable from others. More acoustic features such as spectral tilt and formant transition in the diphthongs and the effects of acoustic features on vowel perception by native English listeners will be discussed. Furthermore, the relationship between the vowel intelligibility and the second language experience of non-native talkers will be examined.