Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> English consonant recognition in undegraded and degraded listening conditions was compared for listeners whose primary language was either Japanese or American English. There were ten subjects in each of the two groups, termed the non-native (Japanese) and the native (American) subjects, respectively. The Modified Rhyme Test was degraded either by a babble of voices (S/N = -3 dB) or by a room reverberation (reverberation time, T = 1.2 s). The Japanese subjects performed at a lower level than the American subjects in both noise and reverberation, although the performance difference in the undegraded, quiet condition was relatively small. There was no difference between the scores obtained in noise and in reverberation for either group. A limited-error analysis revealed some differences in type of errors for the groups of listeners. Implications of the results are discussed in terms of the effects of degraded listening conditions on non-native listeners' speech perception. <s> BIB001 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> This study examined the recognition of English words by groups of native speakers of Italian who differed in age of arrival in Canada and amount of continued native language use. The dependent variable was the number of words correctly repeated in English sentences presented in noise. Significantly higher word recognition scores were obtained for early than late bilinguals, and for early bilinguals who used Italian seldom than for early bilinguals who used Italian relatively often. A hierarchical regression analysis showed that the native Italian participants' ability to perceive English vowels and consonants accounted for a significant amount of variance in the word-recognition scores independently of age of arrival, amount of L1 use, and length of residence in Canada. The native language use effect was interpreted to have arisen from differences in the extent to which the early bilinguals' Italian phonetic system influenced the representations they developed for English vowels and consonants. <s> BIB002 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> Our previous work (Hazan & Simpson, 1998) has shown that increasing the salience of perceptually important regions of nonsense word and sentence materials aids speech perception in noise. This study aimed to extend these findings by investigating the robustness of these enhancement techniques in improving consonant intelligibility for a range of different speakers and for groups of listeners with different language backgrounds. In Experiment 1, nonsense vowel- consonant-vowel (VCV) tokens produced by two female and two male speakers without phonetic training were annotated to highlight segments of the signal corresponding to the consonant constriction/occlusion and vowel onset/offset regions. These regions were selectively amplified to enhance the cues they contained, then combined with speech - shaped noise at 0 dB SNR and presented to normally hearing listeners. Significant improvements in intelligibility were found for all speakers although the extent of the improvement varied across speakers. In Experiment 2, a subset of these stimuli were presented to two groups of learners of English — a Japanese- L1 group and a Spanish - L1 group — and a new group of native- English controls. Results showed a significant effect of enhancement in all listener- groups and similar speaker effects for the non- native and native English listeners. Error patterns were related to the distance between the phonological systems of listeners’ L1 and L2. <s> BIB003 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> Abstract This study investigated the interaction of the L1 and L2 systems in bilinguals by assessing the effect of L1 use on L1 and L2 production accuracy. A novel design feature of this study is that it examined bilinguals who used their L1 on a regular basis in a bilingual setting: Otavalo, Ecuador. Thirty native Quichua speakers who were matched for age of Spanish acquisition were recruited to form three groups differing in self-reported L1 use. The three groups repeated aurally presented sentences from their L1 and L2. Monolingual listeners from each language rated the blocked, randomly presented sentences for degree of foreign accent. For the Spanish sentences, the group with the highest L1 use had stronger Quichua accents than the group with the lowest L1 use. On the other hand, L1 use had no effect on the ratings of the Quichua sentences. Results from an analysis of Korean–English bilinguals are also reported. These results replicate the finding that L1 use affects L2, but not L1 production. These findings indicate that the interaction of the L1 and L2 systems affects the success of L2 acquisition, providing evidence that factors other than neurological maturation influence L2 acquisition. <s> BIB004 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> This study examined the identification of English consonants in noise by native speakers of Italian. The effect of age of first exposure to English was evaluated by comparing three groups of subjects <s> BIB005 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> Previous research has suggested that child but not adult immigrants to the United States and ::: Canada make regular progress learning English as their length of residence (LOR) increases. If ::: children and adults received the same kind of second language (L2) input, such evidence would ::: support the existence of a critical period for L2 acquisition. The present study compared groups ::: of Chinese adults living in the United States who differed in LOR in order to assess the role of ::: input in adults' naturalistic acquisition of an L2. We assessed the Chinese ::: participants' identification of word-final English consonants (experiment 1), their scores on ::: a 144-item grammaticality judgment test (experiment 2), and their scores on a 45-item listening ::: comprehension test (experiment 3). The Chinese participants were assigned to one of four groups ::: ( n = 15 each) based on LOR in the United States and their primary occupation ::: (students vs. nonstudents). Significantly higher scores were obtained for the students with ::: relatively long LORs than for the students with relatively short LORs in all three experiments. ::: However, the difference between the nonstudents differing in LOR was nonsignificant in each ::: instance. The results suggested that the lack of an effect of LOR in some previous studies may ::: have been due to sampling error. It appears that adults' performance in an L2 will improve ::: measurably over time, but only if they receive a substantial amount of native speaker input. <s> BIB006 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> This study examined the production of English /b/ and the perception of short-lag English /b d g/ tokens by four groups of bilinguals who differed according to their age of arrival (AOA) in Canada from Italy and amount of self-reported native language (L1) use. A clear difference emerged between early bilinguals (mean AOA=8 years) and late bilinguals (mean AOA=20 years). The late bilinguals showed a stronger L1 influence than the early bilinguals did on both the production and perception of English stops. In experiment 2, the late bilinguals produced a larger percentage of prevoiced English /b/ tokens than early bilinguals and native English (NE) speakers did. In experiment 3, the late bilinguals misidentified short-lag English /b d g/ tokens as /p t k/ more often than the early bilinguals and NE speakers did. Experiment 4 revealed that the frequencies with which the bilinguals prevoiced /b d g/ in Italian and English were correlated. The observed differences between the early and late bilinguals were att... <s> BIB007 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> Native American English and non-native (Dutch) listeners identified either the consonant or the vowel in all possible American English CV and VC syllables. The syllables were embedded in multispeaker babble at three signal-to-noise ratios (0, 8, and 16 dB). The phoneme identification performance of the non-native listeners was less accurate than that of the native listeners. All listeners were adversely affected by noise. With these isolated syllables, initial segments were harder to identify than final segments. Crucially, the effects of language background and noise did not interact; the performance asymmetry between the native and non-native groups was not significantly different across signal-to-noise ratios. It is concluded that the frequently reported disproportionate difficulty of non-native listening under disadvantageous conditions is not due to a disproportionate increase in phoneme misidentifications. <s> BIB008 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> Recent evidence on the perceptual performance of bilingual listeners suggests that a nonaudibility-based cost exists in processing a second language. That is, when compared to monolingual English speakers and early bilinguals, listeners who acquired English as a second language after puberty show reduced performance when listening to the second language in background noise, despite normal auditory thresholds. However, past studies have not controlled for the homogeneity of the bilingual participants used in auditory research; therefore, it is unknown whether the deficit observed in bilingual function is due to a lack of control for language-related variables. The ability of a homogeneous group of Spanish-English bilinguals and English monolingual listeners to perceive sentences in quiet and in noise at threshold levels was evaluated using the Hearing in Noise Test (HINT). Both groups performed similarly in quiet conditions. In the noise conditions, the bilingual group's performance was significantly poorer than the monolingual group's performance. However, both groups showed a binaural advantage of 7-8 dB when the signal and noise were separated by 90 degrees. <s> BIB009 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> Effects of perceptual and cognitive loads on spoken-word recognition have so far largely escaped investigation. This study lays the foundations of a psycholinguistic approach to speech recognition in adverse conditions that draws upon the distinction between energetic masking, i.e., listening environments leading to signal degradation, and informational masking, i.e., listening environments leading to depletion of higher-order, domain-general processing resources, independent of signal degradation. We show that severe energetic masking, such as that produced by background speech or noise, curtails reliance on lexical-semantic knowledge and increases relative reliance on salient acoustic detail. In contrast, informational masking, induced by a resource-depleting competing task (divided attention or a memory load), results in the opposite pattern. Based on this clear dissociation, we propose a model of speech recognition that addresses not only the mapping between sensory input and lexical representations, as traditionally advocated, but also the way in which this mapping interfaces with general cognition and non-linguistic processes. <s> BIB010 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> Non-rhotic British English speakers and Germans living in England were compared in their use of short- and long-domain r-resonances (cues to an upcoming [@?]) in read English sentences heard in noise. The sentences comprised 52 pairs differing only in /r/ or /l/ in a minimal-pair target word (mirror, miller). Target words were cross-spliced into a different utterance of the same sentence-base (match) and into a base originally containing the other target word (mismatch), making a four-stimulus set for each sentence-pair. Intelligibility of target and some preceding unspliced words was measured. English listeners were strongly influenced by r-resonances in the sonorant immediately preceding the critical /r/. A median split of the German group showed that those who had lived in southeast England for 3-20 months used the weaker long-domain r-resonances, whereas Germans who had lived in England for 21-105 months ignored all r-resonances, possibly in favour of word frequency. A preliminary study of German speech showed differences in temporal extent and spectral balance (frequency of F3 and higher formants) between English and German r-resonances. The perception and production studies together suggest sophisticated application of exposure-induced changes in acoustic-phonetic and phonological knowledge of L1 to a partially similar sound in L2. <s> BIB011 </s> Non-native speech perception in adverse conditions: A review <s> Influence of L1 and AOA <s> Processing speech in a non-native language requires listeners to cope with influences from their first language and to overcome the effects of limited exposure and experience. These factors may be particularly important when listening in adverse conditions. However, native listeners also suffer in noise, and the intelligibility of speech in noise clearly depends on factors which are independent of a listener's first language. The current study explored the issue of language-independence by comparing the responses of eight listener groups differing in native language when confronted with the task of identifying English intervocalic consonants in three masker backgrounds, viz. stationary speech-shaped noise, temporally-modulated speech-shaped noise and competing English speech. The study analysed the effects of (i) noise type, (ii) speaker, (iii) vowel context, (iv) consonant, (v) phonetic feature classes, (vi) stress position, (vii) gender and (viii) stimulus onset relative to noise onset. A significant degree of similarity in the response to many of these factors was evident across all eight language groups, suggesting that acoustic and auditory considerations play a large role in determining intelligibility. Language-specific influences were observed in the rankings of individual consonants and in the masking effect of competing speech relative to speech-modulated noise. <s> BIB012
Some studies which fall under the criteria of the present review had the goal of investigating the predictions made by the models of non-native speech perception described in Section 3.2. In those studies, noise is used to elicit differences in perceptual competence between populations which may not surface in quiet conditions. Flege and his collaborators tested the SLM using pink noise to avoid ceiling performance effects and explore in more detail subtle differences between monolingual and bilingual listeners (Mackay et al., 2001a,b; BIB002 BIB006 . BIB003 looked at the effect of systemic differences between the L1 and the FL (finding, against their predictions, poor perceptual results also for sounds which are shared by the two languages). Van Dommelen and analysed consonant perception to observe the effect of adverse conditions on novel sounds versus sounds which exist in both language inventories, applying a category goodness fit criterion as suggested in PAM. Again, contrary to expectations but agreeing with BIB003 , novel sounds present better discrimination in noise than shared categories, which the authors suggest could be due to differences in phonetic detail between the apparently identical categories. It seems that current L2 perception models do not well predict the results of speech perception in noise. It has been suggested that the weight of the L1 differs according to the stages of acquisition.  model explicitly states that the influence of the L1 is greatest at the initial stages of acquisition and that it decreases as acquisition of the TL sound system progresses. If we see the advance of acquisition as a gain in linguistic competence, we could say that the weight of the L1 sound system is inversely proportional to the level of phonological competence in the TL. BIB003 found L1 interference to be stronger in adverse conditions than in quiet. However, the study by van Dommelen and found no increase in L1-based confusions in noise. The authors suggest that differences in the level of FL competence might explain the conflicting findings: listeners in the later study had a higher FL competence which led to less L1 interference.  proposed a model in which the level of language activation or bilingual 'language mode' affects the quality of speakers' performance. Several studies have investigated the amount of L1 activation and its effect on L2 speech production and perception, based on the idea that a more active L1 system (through more exposure to, and use of, the L1) will have more influence on the L2/ FL. There is evidence indicative of this being the case for L2/FL degree of foreign accent (Flege et al., , 1997 BIB004  . On the other hand,  found no detrimental effect of L1 use on vowel discrimination for two groups of early L2 learners who differed in amount of L1 activation. However, these authors found the same subject groups to differ in consonant identification and word recognition when embedded in pink noise, with an advantage for the group who used the L1 less frequently (Mackay et al., 2001a,b; BIB002 . This is an interesting indication of how simulated adverse conditions might provide the finegrained tool necessary to uncover subtle perceptual phenomena which are not apparent in quiet conditions. Adverse listening conditions may themselves favour a greater L1 influence, since in challenging circumstances listeners might be expected to fall back on familiar categories and cues. Similarly, when insufficient information is available, listener cue use may be appropriate for their L1 categories but not necessarily for the TL BIB011 . Energetic masking (see Section 4.1) has been shown to increase the relative weight of acoustic detail at the expense of lexical-semantic knowledge BIB010 ) which in turn may reduce L2 activation. BIB001 consider that L1-induced confusions rise in degraded conditions. On the other hand, BIB008 and van Dommelen and find that the influence of the native system does not increase in noise relative to less adverse or quiet conditions. Noise seems to induce a good deal of similarity in responses from different listener populations BIB012 . Amount of input has been varied in a number of the studies in Table 1 . BIB005 found differences in stop perception in quiet and noise between bilinguals and L2 learners. BIB007 analysed English consonant perception in noise for three groups of L2 speakers who differed in their learning starting age, finding that early learners showed an advantage for onset consonant identification but not for coda consonants. More research is needed to elucidate the possible effect of L2 learning age on perception in adverse conditions. Other studies BIB009  found that the age at which the L2 exposure started is inversely correlated with performance in a L1 in noise perception test; that is, earlier bilinguals performed worse than late bilinguals in their L1, which is a sign of loss of competence in the L1 due to L2 interference. Finally, BIB006 presented final plosives for discrimination embedded in different levels of noise to Chinese listeners differing in length of residence in the TL country and in their occupation during their stay (students versus workers). Length of residence produced significant perceptual differences in two student groups but not in two worker groups, a lack of effect ascribed to the smaller amount of TL input for the latter groups. BIB005 find differences in short-lag voiced plosive perception between native listeners and (early) bilinguals versus late bilinguals who have a more active L1 but not for late bilinguals with a less frequent use of the L1. Accordingly, these differences are put down not to age of learning itself but to the differences in quality and quantity of the input in favour of the early learners and less frequent L1 users.