Sentence recognition in native- and foreign-language multi-talker background noise

Studies of speech perception in various types of background noise have shown that noise with linguistic content affects listeners differently than nonlinguistic noise [e.g., Simpson, S. A., and Cooke, M. (2005). "Consonant identification in N-talker babble is a nonmonotonic function of N," J. Acoust. Soc. Am. 118, 2775-2778; Sperry, J. L., Wiley, T. L., and Chial, M. R. (1997). "Word recognition performance in various background competitors," J. Am. Acad. Audiol. 8, 71-80] but few studies of multi-talker babble have employed background babble in languages other than the target speech language. To determine whether the adverse effect of background speech is due to the linguistic content or to the acoustic characteristics of the speech masker, this study assessed speech-in-noise recognition when the language of the background noise was either the same or different from the language of the target speech. Replicating previous findings, results showed poorer English sentence recognition by native English listeners in six-talker babble than in two-talker babble, regardless of the language of the babble. In addition, our results showed that in two-talker babble, native English listeners were more adversely affected by English babble than by Mandarin Chinese babble. These findings demonstrate informational masking on sentence-in-noise recognition in the form of "linguistic interference." Whether this interference is at the lexical, sublexical, and/or prosodic levels of linguistic structure and whether it is modulated by the phonetic similarity between the target and noise languages remains to be determined.     

Sequential calculations for heavy-ion induced two-nucleon transfer on 14N, 15N and 16O

¹¹B and ¹³C induced two-nucleon transfer data on ¹⁴N, ¹⁵N and ¹⁶O are compared with exact finite-range sequential transfer calculations. The data appear to be consistent with this reaction model and the assumed shell-model structure of the states populated. Single-nucleon transfer data on these targets is also analyzed using the DWBA. Modifications to the exit channel optical potential are required to obtain agreement with shell-model spectroscopic factors.     

The clear speech effect for non-native listeners

Previous work has established that naturally produced clear speech is more intelligible than conversational speech for adult hearing-impaired listeners and normal-hearing listeners under degraded listening conditions. The major goal of the present study was to investigate the extent to which naturally produced clear speech is an effective intelligibility enhancement strategy for non-native listeners. Thirty-two non-native and 32 native listeners were presented with naturally produced English sentences. Factors that varied were speaking style (conversational versus clear), signal-to-noise ratio (-4 versus -8 dB) and talker (one male versus one female). Results showed that while native listeners derived a substantial benefit from naturally produced clear speech (an improvement of about 16 rau units on a keyword-correct count), non-native listeners exhibited only a small clear speech effect (an improvement of only 5 rau units). This relatively small clear speech effect for non-native listeners is interpreted as a consequence of the fact that clear speech is essentially native-listener oriented, and therefore is only beneficial to listeners with extensive experience with the sound structure of the target language.     

The interlanguage speech intelligibility benefit

This study investigated how native language background influences the intelligibility of speech by non-native talkers for non-native listeners from either the same or a different native language background as the talker. Native talkers of Chinese (n = 2), Korean (n = 2), and English (n = 1) were recorded reading simple English sentences. Native listeners of English (n = 21), Chinese (n = 21), Korean (n = 10), and a mixed group from various native language backgrounds (n = 12) then performed a sentence recognition task with the recordings from the five talkers. Results showed that for native English listeners, the native English talker was most intelligible. However, for non-native listeners, speech from a relatively high proficiency non-native talker from the same native language background was as intelligible as speech from a native talker, giving rise to the "matched interlanguage speech intelligibility benefit." Furthermore, this interlanguage intelligibility benefit extended to the situation where the non-native talker and listeners came from different language backgrounds, giving rise to the "mismatched interlanguage speech intelligibility benefit." These findings shed light on the nature of the talker-listener interaction during speech communication.     

Semantic and phonetic enhancements for speech-in-noise recognition by native and non-native listeners

Previous research has shown that speech recognition differences between native and proficient non-native listeners emerge under suboptimal conditions. Current evidence has suggested that the key deficit that underlies this disproportionate effect of unfavorable listening conditions for non-native listeners is their less effective use of compensatory information at higher levels of processing to recover from information loss at the phoneme identification level. The present study investigated whether this non-native disadvantage could be overcome if enhancements at various levels of processing were presented in combination. Native and non-native listeners were presented with English sentences in which the final word varied in predictability and which were produced in either plain or clear speech. Results showed that, relative to the low-predictability-plain-speech baseline condition, non-native listener final word recognition improved only when both semantic and acoustic enhancements were available (high-predictability-clear-speech). In contrast, the native listeners benefited from each source of enhancement separately and in combination. These results suggests that native and non-native listeners apply similar strategies for speech-in-noise perception: The crucial difference is in the signal clarity required for contextual information to be effective, rather than in an inability of non-native listeners to take advantage of this contextual information per se.     

Exotic components of SO(p,q) surface group representations,and their Higgs bundle avatars

For semisimple Lie groups, moduli spaces of Higgs bundles on a Riemann surface correspond to representation varieties for the surface fundamental group. In many cases, natural topological invariants label connected components of the moduli spaces. Hitchin representations into split real forms, and maximal representations into Hermitian Lie groups, are the only previously know cases where natural invariants do not fully distinguish connected components. In this note we announce the existence of new such exotic components in the moduli spaces for the groups $\mathrm{SO}(p,q)$ with $2<p<q$. These groups lie outside formerly know classes of groups associated with exotic components.     

Moduli Spaces of Coherent Systems of Small Slope on Algebraic Curves

Let C be an algebraic curve of genus g ≥ 2. A coherent system on C consists of a pair (E, V), where E is an algebraic vector bundle over C of rank n and degree d and V is a subspace of dimension k of the space of sections of E. The stability of the coherent system depends on a parameter α. We study the geometry of the moduli space of coherent systems for 0 < d ≤ 2n. We show that these spaces are irreducible whenever they are nonempty and obtain necessary and sufficient conditions for nonemptiness.