Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <s> In this study, the effect of linguistic experience on the auditory discrimination of words has been examined. 18 subjects, including 6 native and 12 non-native speakers of English, were tested with CID auditory test W-22 in quiet and in the presence of white noise at the signal-to-noise (S/N) ratios of + 12, + 6 and 0 dB. The non-native speakers of English included 6 with 1 year of experience and 6 with 3–4 years of experience speaking English in the USA.In the absence of noise, the results were essentially equivalent for all three groups. As noise level increased, word discrimination deteriorated for all three groups with non-native speakers of English obtaining results significantly poorer than native speakers of English. Linguistic experience and noise levels were significant at the 0.001 level of confidence. It appears that at 0 dB S/N, individual variability of non-native speakers of English, regardless of their original linguistic background, was much smaller than that found for native speakers of E... <s> BIB001 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <s> Speech perception in reverberation was compared for native English speaking and non‐native listeners. The Modified Rhyme Test was recorded with reverberation times (T) of 0.4, 0.8, and1.2 s. Testing was monaural. The mean word identification scores without reverberation were similar for both groups. With T=0.8 and 1.2 s, non‐native listeners scored 10% lower than the native listeners. These results indicate that non‐native listeners who understand English very well in the absence of reverberation might have difficulty understanding speech in the presence of even moderate reverberation. <s> BIB002 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <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> BIB003 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <s> To determine how age of acquisition influences perception of second-language speech, the Speech Perception in Noise (SPIN) test was administered to native Mexican-Spanish-speaking listeners who lea... <s> BIB004 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <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> BIB005 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <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> BIB006 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <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> BIB007 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <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> BIB008 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <s> 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... <s> BIB009 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <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> BIB010 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <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> BIB011 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <s> In many studies, the influence of intelligibility of the interfering speech is avoided by reversing it in time. Usually, intelligibility with time-reversed interfering speech indeed is higher compared to that with normal interfering speech. However, due to the nature of speech, reversed speech also gives rise to increased forward masking. The latter will result in a decrease in intelligibility. Thus, differences in intelligibility as a consequence of reversing speech in time are due to two opposite effects. This paper describes a speech reception threshold (SRT) test with intelligible and unintelligible interfering speech played normally and time-reversed. With Dutch listeners, Swedish reversed interfering speech gave a rise in SRT of 2.3 dB compared with the Swedish interfering speech (played normally). The difference can be attributed to differences in forward masking. Dutch time-reversed interfering speech gave a decrease in SRT of 4.3 dB compared to (intelligible) Dutch interfering speech. The latter ... <s> BIB012 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <s> This study compared monosyllabic word recognition in quiet, noise, and noise with reverberation for 15 monolingual American English speakers and 12 Spanish–English bilinguals who had learned English prior to 6 years of age and spoke English without a noticeable foreign accent. Significantly poorer word recognition scores were obtained for the bilingual listeners than for the monolingual listeners under conditions of noise and noise with reverberation, but not in quiet. Although bilinguals with little or no foreign accent in their second language are often assumed by their peers, or their clinicians in the case of hearing loss, to be identical in perceptual abilities to monolinguals, the present data suggest that they may have greater difficulty in recognizing words in noisy or reverberant listening environments. <s> BIB013 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <s> Although most research on the perception of speech has been conducted with speech presented without any competing sounds, we almost always listen to speech against a background of other sounds which we are adept at ignoring. Nevertheless, such additional irrelevant sounds can cause severe problems for speech recognition algorithms and for the hard of hearing as well as posing a challenge to theories of speech perception. A variety of different problems are created by the presence of additional sound sources: detection of features that are partially masked, allocation of detected features to the appropriate sound sources and recognition of sounds on the basis of partial information. The separation of sounds is arousing substantial attention in psychoacoustics and in computer science. An effective solution to the problem of separating sounds would have important practical applications. <s> BIB014 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <s> 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. <s> BIB015 </s> Non-native speech perception in adverse conditions: A review <s> Non-native speech perception in adverse conditions <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> BIB016
As we began our review: the effect of noise on speech perception is much greater for non-native than for native listeners, and this has been familiar as long as there have been listeners to a second language. The question was, however, first addressed in the laboratory by  , now nearly half a century ago. Their study compared word reception scores in quiet and white noise at SNRs of +4, 0 and À4 dB. A modest disadvantage for non-native relative to native listeners in quiet of about 11 percentage points grew to 16, 25 and 29 percentage points with increasing noise. Since then, the topic has been explored systematically, especially in the last decade. As already noted, non-native studies on this topic have focused on additive noise sources, with only a few considering reverberation, and only one investigating the combined effect of noise and reverberation BIB013 . Channel distortion has received very little attention apart from an early study by  , while  employed interrupted speech, finding no significant non-native disadvantage. Two further aspects of real speech usage are similarly absent from most studies, namely the effect of communicative context and noise on speech production (see, e.g.,   for recent summaries). The effects of noise, reverberation and channel distortion on speech perception and production by native listeners are examined in detail in  , while BIB014 provides a comprehensive review of listening to speech in the presence of other sounds, including the special case of interfering speech maskers. Table 1 lists many of the published articles (but excluding those in the current Special Issue) addressing nonnative speech perception in adverse conditions. Some commonalities and trends are evident in this table. English is nearly always used as the target language, perhaps raising a question concerning applicability of findings to other languages, particularly to those with tone-based distinctions. The type of noise employed has changed over the years, with predominantly white or pink noise giving way to speech-shaped noise and more informative maskers such as low-order babble and competing talkers. Tasks have varied from low-level consonant determination to the identification of keywords in low/high predictability sentences. Several types of factor are at play in determining nonnative listener performance in the studies listed in Table 1 : (i) listener factors such as exposure, L2 competence and age of acquisition; (ii) noise factors such as type and level of noise or reverberation; and (iii) task factors which define the amount and kind of speech processing knowledge required to identify consonants, words or sentences. We return to the explanatory weight of these factors in Section 6. In the present section we describe the empirical studies, grouped principally by type of noise, but we begin with a summary of the principal findings. Non-native listeners suffer more from increasing noise than natives when the task involves words  BIB001 or sentences  BIB005 but for tasks which minimise or eliminate the possibility of using high-level linguistic information, noise has an equivalent overall effect on native and non-native listeners BIB007 MacKay et al., 2001a,b; BIB010 BIB013 . There are indications that reverberation affects nonnative listeners more than natives for low-level tasks involving consonant identification BIB002 BIB003 . Intelligible maskers in an L2 appear to reduce L1 interference and hence aid non-native listeners BIB012 García Lecumberri and Cooke, 2006; BIB015 . However, competing speech in the background increases overall informational masking for non-natives more than for natives BIB016 . In noise, early bilinguals are better than later L2 learners in the perception of sentences BIB004  , words BIB005 and segments (Mackay et al., 2001a,b) , though not for all positions BIB006 . Even bilinguals from infancy manifest differences in speech perception in noise as compared to monolinguals, although these differences are not apparent in quiet nor in speech production BIB004 BIB011 . The bilingualmonolingual difference is not observed if the bilinguals use the other language less frequently BIB006 . Some of the errors found in speech in noise tasks are due to the influence of the L1 sound system BIB008 García Lecumberri and Cooke, 2006) , and the relative degree of activation of the L1 correlates with the strength of its influence BIB005 Mackay et al., 2001a,b) . Performance in speech perception tasks in adverse conditions correlates with the quality and quantity of input BIB004 BIB013 Mackay et al., 2001a,b; BIB005 BIB009  .