Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <s> Sixteen English consonants were spoken over voice communication systems with frequency distortion and with random masking noise. The listeners were forced to guess at every sound and a count was made of all the different errors that resulted when one sound was confused with another. With noise or low‐pass filtering the confusions fall into consistent patterns, but with high‐pass filtering the errors are scattered quite randomly. An articulatory analysis of these 16 consonants provides a system of five articulatory features or “dimensions” that serve to characterize and distinguish the different phonemes: voicing, nasality, affrication, duration, and place of articulation. The data indicate that voicing and nasality are little affected and that place is severely affected by low‐pass and noisy systems. The indications are that the perception of any one of these five features is relatively independent of the perception of the others, so that it is as if five separate, simple channels were involved rather tha... <s> BIB001 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <s> Materials are presented for a test of word identification in which the cues for response are confined to the initial consonants and consonant‐vowel transitions. Some preliminary results are discussed. <s> BIB002 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <s> Consonant confusion matrices were obtained for four sets of CV and VC nonsense syllables presented both in quiet and in the presence of a masking noise. A sequential method of partitioning transmitted information for confusion matrices was developed and used to test the hypothesis that when the internal redundancy of feature systems is taken into account, certain articulatory and phonological features of consonants consistently account for transmitted information better than other, closely related, features. Results of the analyses indicate that for most confusion matrices several feature systems can be shown to account equally well for transmitted information, and that across syllable sets and listening conditions, there is little consistency in the identification of perceptually important features. The implication of these findings with respect to the existence of natural perceptual features for consonants is discussed. <s> BIB003 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <s> ABSTRACf This artil;le examines the perception of four English vowels (Ii, I, e, reI) by adult native speakers of German. From the standpoint of German, it appears that English Ii, I, £I are perceptually similar, if not identical, to German Ii, I, £I, whereas lrel is a "new" vowel for German learners of English. The role of foreign language experience in the perception of second language vowels was examined through labeling responses to members of synthetic continua (beat-bit, bet-bat) in which vowel duration and spectrum were varied factorily. The subjects were relatively experi­ enced and inexperienced second language (L2) learners and a monolingual English control group. The results suggest that L2 experience did not affect perception for the continuum with the two "similar" vowels IiI and III. However, for the continuum involving the "new" vowel lrel, the experienced Germans more closely resembled the native English speakers than the inexperi­ enced Germans. The predominant use of duration cues in differentiating the English Id-/rel contrast by the inexperienced Germans suggested that when spectra] cues are insufficient to differentiate an L2 vowel contrast, duration will be used. The hypothesis tested in the present study was derived from a model of second language (L2) speech learning that distinguishes between identical, similar, and new sounds in a cross-language context (see Flege, 1987, 1988; Flege & Hillenbrand, 1984). Identical sounds (e.g., English and German Im/) are unlikely to pose a learning problem, but similar sounds like English and German lul might offer persistent, if perhaps only subtle, problems for L2 learners. The hypothesis being tested states that adult L2learners will substi­ tute a sound from their first language (Ll) for a similar L2 sound even after extended L2 exposure because of equivalence classification. On the other hand, the model hypothesizes that for new L2 sounds (e.g., English Irl for Ll German learners) that exceed a yet-to-be-specified "crucial similarity measure" (Wode, 1977), learners will eventually establish new phonetic cate­ gories as a result of phonetic learning that is unimpeded by equivalence classification. Although the sounds of German and English have been examined thor <s> BIB004 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <s> A group of Spanish- and English-speaking listeners participated in a multidimensional scaling (MDS) study examining perceptual responses to three Spanish and seven English vowels. The vowel stimuli represented tokens of Spanish /i/, /e/, and /a/ and English /i/, /I/, /eI/, /epsilon/, /ae/, /lambda/, and /a/. Each vowel had been spoken by three monolingual talkers of Spanish or English and all possible vowel pairs (405 pairs) were presented to listeners (excluding pairs representing the same vowel category). Thirty monolingual English listeners and thirty native Spanish listeners who had learned English as a second language rated these vowel pairs on a nine-point dissimilarity scale. These perceptual distances were then analyzed using then individual-differences version of ALSCAL. Results demonstrated that the English monolinguals used three underlying dimensions in rating vowels while the Spanish-English bilinguals used just two. The most salient perceptual dimension for both groups distinguished vowel height. However, for the English listeners, this dimension was most significantly correlated with duration and indicated a language-dependent sensitivity to this phonetic feature. The second dimension for the English listeners represented a front-back distinction, while the third reflected a central/noncentral distinction. For the Spanish listeners, the second dimension was less easily interpreted. However, the perceptual data for the Spanish listeners was more interpretable in terms of the distribution of the vowels in the two-dimensional perceptual plane. The vowels were distributed in terms of three separate vowel clusters, each cluster near the location of a Spanish vowel.(ABSTRACT TRUNCATED AT 250 WORDS) <s> BIB005 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <s> Abstract Two sets of experiments were performed to test the perceptual benefits of enhancing consonantal regions which contain a high density of acoustic cues to phonemic contrasts. In the first set, hand-annotated consonantal regions of natural vowel–consonant–vowel (VCV) stimuli were amplified to increase their salience, and filtered to stylise the cues they contained. In the second set, corresponding regions in natural semantically-unpredictable sentence (SUS) material were annotated and enhanced in the same way. Both sets of stimuli were combined with speech-shaped noise and presented to normally-hearing listeners. The VCV experiments showed statistically significant improvements in intelligibility as a result of enhancement; significant improvements were also obtained for sentence material after some adjustments in enhancement strategies and levels. These results demonstrate the benefits gained from enhancement techniques which use knowledge of acoustic cues to phonetic contrasts to improve the intelligibility of speech in the presence of background noise. <s> BIB006 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <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> BIB007 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <s> Previous studies [Lisker, J. Acoust. Soc. Am. 57, 1547–1551 (1975); Summerfield and Haggard, J. Acoust. Soc. Am. 62, 435–448 (1977)] have shown that voice onset time (VOT) and the onset frequency of the first formant are important perceptual cues of voicing in syllable-initial plosives. Most prior work, however, has focused on speech perception in quiet environments. The present study seeks to determine which cues are important for the perception of voicing in syllable-initial plosives in the presence of noise. Perceptual experiments were conducted using stimuli consisting of naturally spoken consonant-vowel syllables by four talkers in various levels of additive white Gaussian noise. Plosives sharing the same place of articulation and vowel context (e.g., ∕pa,ba∕) were presented to subjects in two alternate forced choice identification tasks, and a threshold signal-to-noise-ratio (SNR) value (corresponding to the 79% correct classification score) was estimated for each voiced/voiceless pair. The threshol... <s> BIB008 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <s> The difficulty of listening to speech in noise is exacerbated when the speech is in the listener’s L2 rather than L1. In this study, Spanish and Dutch users of English as an L2 identified American English consonants in a constant intervocalic context. Their performance was compared with that of L1 (British English) listeners, under quiet conditions and when the speech was masked by speech from another talker or by noise. Masking affected performance more for the Spanish listeners than for the L1 listeners, but not for the Dutch listeners, whose performance was worse than the L1 case to about the same degree in all conditions. There were, however, large differences in the pattern of results across individual consonants, which were consistent with differences in how consonants are identified in the respective L1s. Index Terms: speech perception, consonants, noise, L1, L2 <s> BIB009 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <s> The aim of this study was to investigate factors that affect second language speech perception. Listening tests were run in which native and non-native (Norwegian) participants identified English consonants in VCV syllables in quiet and in different noise conditions. An assimilation test investigated the mapping of English consonants onto Norwegian counterparts. Results of the identification test showed a lower non-native performance but there was no evidence that the non-native disadvantage was greater in noise than in quiet. Poorer identification was found for sounds that occur only in English ('novel category' consonants) but this was the case for both English and Norwegian listeners, and thus likely to be related to the acoustic-phonetic properties of consonants in that category. Information transfer analyses revealed a certain impact of phonological factors on L2 perception, as the transmission of the voicing feature was more affected for Norwegian listeners than the transmission of place or manner information. The relation between the results of the identification in noise and assimilation tasks suggests that, at least in higher proficiency L2 learners, assimilation patterns may not be predictive of listeners' ability to hear non-native speech sounds. <s> BIB010 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <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> BIB011 </s> Non-native speech perception in adverse conditions: A review <s> Noise and non-native phonetic cue perception <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> BIB012
For tasks which involve making segmental distinctions (e.g., from nonsense or rhyming words, alone or in sen-tence context), phonetic feature analysis allows a more detailed comparison of native-and non-native listener performance in noise. Feature analysis operates directly for tasks such as the diagnostic rhyme test BIB002 , where word pairs differ in a single feature such as voicing or place, or indirectly from consonant or vowel discrimination tasks where the proportion of transmitted information (TI) for each feature can be derived from the confusion matrix BIB001 BIB003 . BIB001 reported that TI values for voicing and nasality survived noise better than affrication and durational features, with place-based confusions being most adversely-affected. However, a recent repetition by  found a substantially different feature ranking, with voicing worse than place in noise, a finding echoed by BIB010 and BIB011 . Many studies agree that sibilance is particularly robust in noise BIB001 BIB003  BIB011 . BIB003 highlighted the importance of position in the syllable for consonant perception in noise. BIB006 found that voice was by far the best transmitted feature in noise followed by manner and lastly by place. They suggest that manner confusions between plosives and fricatives are particularly frequent in noise and that the best cues for place are bursts for plosives, the frequency of fricative noise for fricatives and in general F2 and F3 transitions to following vowels. BIB008 looked at factors and cues for plosive voicing distinction in noise. Whilst VOT duration was the best voicing cue in quiet conditions, the context /Ca/ promoted greatest intelligibility in noise, perhaps related to the fact that F1 onset is a good cue for voicing contrasts in noise. Additionally they found that plosive burst and aspiration are easily masked by noise, that F0 is not an important cue in noise and that the contrast is least robust in the case of bilabial plosives. Comparisons of native and non-native sound perception demonstrate that native listeners use different cues and cue weightings and that non-natives' cue use comes to resemble the native pattern as competence in the L2 advances BIB004 BIB005  Flege et al., 1997;  . Given that native listeners use different cues and cue rankings in noise compared to quiet, and that non-native listeners differ from natives also in the relative use of cues, it is reasonable to assume that NN will use different cues to natives in noise. However, it could be that noise induces the use of universal robust cues, leading to greater similarity in cue use in noise compared to quiet. Indeed, several recent studies in noise (e.g. BIB011 BIB010 have suggested the presence of universal acoustic confusions, which may be less apparent in quiet due to ceiling effects. In practice, a mixture of L1-influences and language-independent effects are evident. Spanish listeners suffered from poor voice reception in BIB007 compared to Japanese and English listeners, presumably due to the absence of voiced fricative phonemes in Spanish, but place was the least well transmitted feature for all three L1 groups, pointing to a basis in acoustic masking. BIB009 suggest that the effect of noise on native versus non-native cue use may differ depending on the relevance of the cue in the L1. In particular, they showed that the differential reliance on transitional cues, which are more fragile in noise, could explain the considerable drop in fricative performance for both native (English) and non-native (Spanish) listeners, who use these cues in their L1s for fricative distinctions. The other non-native group tested (Dutch), whose fricative inventory does not require these cues, was relatively less affected by noise. BIB012 also show differential use of cues in noise, in their case short and long-term r-resonances. While native English listeners experienced a strong facilitating effect of r-resonances in English sentences, only those German listeners with relatively little experience in English were able to exploit the long-term cues, while Germans with more experience in English ignored them.