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The current study investigated the phonetic adjustment mechanisms that underlie perceptual adaptation in first and second language (Dutch-English) listeners by exposing them to a novel English accent containing controlled deviations from the standard accent (e.g. /i/-to-/ɪ/ yielding /krɪm/ instead of /krim/ for ‘cream’). These deviations involved contrasts that either were contrastive or were not contrastive in Dutch. Following accent exposure with disambiguating feedback, listeners completed lexical decision and word identification tasks. Both native and second language listeners demonstrated adaptation, evidenced by higher lexical endorsement rates and word identification accuracy than untrained control listeners for items containing trained accent patterns. However, for L2 listeners, adaptation was modulated by the phonemic contrast, that is, whether or not it was contrastive in the listeners’ native language. Specifically, the training-induced criterion loosening for the L2 listeners was limited to contrasts that exist in both their L1, Dutch, and L2, English. For contrasts that are either absent or neutralized in Dutch, the L2 listeners demonstrated relatively loose pre-training criteria compared to L1 listeners. The results indicate that accent exposure induces both a general increase in tolerance for atypical speech input as well as targeted adjustments to specific categories for both L1 and L2 listeners.

Second-language (L2) speech is consistently slower than first-language (L1) speech, and L1 speaking rate varies within- and across-talkers depending on many individual, situational, linguistic, and sociolinguistic factors. It is asked whether speaking rate is also determined by a language-independent talker-specific trait such that, across a group of bilinguals, L1 speaking rate significantly predicts L2 speaking rate. Two measurements of speaking rate were automatically extracted from recordings of read and spontaneous speech by English monolinguals (n = 27) and bilinguals from ten L1 backgrounds (n = 86): speech rate (syllables/second), and articulation rate (syllables/second excluding silent pauses). Replicating prior work, L2 speaking rates were significantly slower than L1 speaking rates both across-groups (monolinguals' L1 English vs bilinguals' L2 English), and across L1 and L2 within bilinguals. Critically, within the bilingual group, L1 speaking rate significantly predicted L2 speaking rate, suggesting that a significant portion of inter-talker variation in L2 speech is derived from inter-talker variation in L1 speech, and that individual variability in L2 spoken language production may be best understood within the context of individual variability in L1 spoken language production.

Adaptation to foreign-accented sentences can be guided by knowledge of the lexical content of those sentences, which, being an exact match for the target, provides feedback on all linguistic levels. The extent to which this feedback needs to match the accented sentence was examined by manipulating the degree of match on different linguistic dimensions, including sub-lexical, lexical, and syntactic levels. Conditions where target-feedback sentence pairs matched and mismatched generated greater transcription improvement over non-English speech feedback, indicating listeners can draw upon sources of linguistic information beyond matching lexical items, such as sub- and supra-lexical information, during adaptation.

This study examined the influence of background language variation on speech recognition. English listeners performed an English sentence recognition task in either “pure” background conditions in which all trials had either English or Dutch background babble or in mixed background conditions in which the background language varied across trials (i.e., a mix of English and Dutch or one of these background languages mixed with quiet trials). This design allowed the authors to compare performance on identical trials across pure and mixed conditions. The data reveal that speech-in-speech recognition is sensitive to contextual variation in terms of the target-background language (mis)match depending on the relative ease/difficulty of the test trials in relation to the surrounding trials.

Background: Masking release for an English sentence-recognition task in the presence of foreign-accented English speech compared with native-accented English speech was reported in Calandruccio et al (2010a). The masking release appeared to increase as the masker intelligibility decreased. However, it could not be ruled out that spectral differences between the speech maskers were influencing the significant differences observed. Purpose: The purpose of the current experiment was to minimize spectral differences between speech maskers to determine how various amounts of linguistic information within competing speech affect masking release. Research Design: A mixed-model design with within-subject (four two-talker speech maskers) and between-subject (listener group) factors was conducted. Speech maskers included native-accented English speech and high-intelligibility, moderate-intelligibility, and low-intelligibility Mandarin-accented English. Normalizing the long-term average speech spectra of the maskers to each other minimized spectral differences between the masker conditions. Study Sample: Three listener groups were tested, including monolingual English speakers with normal hearing, nonnative English speakers with normal hearing, and monolingual English speakers with hearing loss. The nonnative English speakers were from various native language backgrounds, not including Mandarin (or any other Chinese dialect). Listeners with hearing loss had symmetric mild sloping to moderate sensorineural hearing loss. Data Collection and Analysis: Listeners were asked to repeat back sentences that were presented in the presence of four different two-talker speech maskers. Responses were scored based on the key words within the sentences (100 key words per masker condition). A mixed-model regression analysis was used to analyze the difference in performance scores between the masker conditions and listener groups. Results: Monolingual English speakers with normal hearing benefited when the competing speech signal was foreign accented compared with native accented, allowing for improved speech recognition. Various levels of intelligibility across the foreign-accented speech maskers did not influence results. Neither the nonnative English-speaking listeners with normal hearing nor the monolingual English speakers with hearing loss benefited from masking release when the masker was changed from native-accented to foreign-accented English. Conclusions: Slight modifications between the target and the masker speech allowed monolingual English speakers with normal hearing to improve their recognition of native-accented English, even when the competing speech was highly intelligible. Further research is needed to determine which modifications within the competing speech signal caused the Mandarin-accented English to be less effective with respect to masking. Determining the influences within the competing speech that make it less effective as a masker or determining why monolingual normal-hearing listeners can take advantage of these differences could help improve speech recognition for those with hearing loss in the future.

Foreign-accented speech can be difficult to understand but listeners can adapt to novel talkers and accents with appropriate experience. Previous studies have demonstrated talker-independent but accent-dependent learning after training on multiple talkers from a single language background. Here, listeners instead were exposed to talkers from five language backgrounds during training. After training, listeners generalized their learning to novel talkers from language backgrounds both included and not included in the training set. These findings suggest that generalization of foreign-accent adaptation is the result of exposure to systematic variability in accented speech that is similar across talkers from multiple language backgrounds.

Children with dyslexia often exhibit increased variability in sensory and cognitive aspects of hearing relative to typically developing peers. Assistive listening devices (classroom FM systems) may reduce auditory processing variability by enhancing acoustic clarity and attention. We assessed the impact of classroom FM system use for 1 year on auditory neurophysiology and reading skills in children with dyslexia. FM system use reduced the variability of subcortical responses to sound, and this improvement was linked to concomitant increases in reading and phonological awareness. Moreover, response consistency before FM system use predicted gains in phonological awareness. A matched control group of children with dyslexia attending the same schools who did not use the FM system did not show these effects. Assistive listening devices can improve the neural representation of speech and impact reading-related skills by enhancing acoustic clarity and attention, reducing variability in auditory processing.

This article presents a review of the effects of adverse conditions (ACs) on the perceptual, linguistic, cognitive, and neurophysiological mechanisms underlying speech recognition. The review starts with a classification of ACs based on their origin: Degradation at the source (production of a noncanonical signal), degradation during signal transmission (interfering signal or medium-induced impoverishment of the target signal), receiver limitations (peripheral, linguistic, cognitive). This is followed by a parallel, yet orthogonal classification of ACs based on the locus of their effect: Perceptual processes, mental representations, attention, and memory functions. We then review the added value that ACs provide for theories of speech recognition, with a focus on fundamental themes in psycholinguistics: Content and format of lexical representations, time-course of lexical access, word segmentation, feed-back in speech perception and recognition, lexicalsemantic integration, interface between the speech system and general cognition, neuroanatomical organisation of speech processing. We conclude by advocating an approach to speech recognition that includes rather than neutralises complex listening environments and individual differences.

The goal of the present study was to devise a means of representing languages in a perceptual similarity space based on their overall phonetic similarity. In Experiment 1, native English listeners performed a free classification task in which they grouped 17 diverse languages based on their perceived phonetic similarity. A similarity matrix of the grouping patterns was then submitted to clustering and multidimensional scaling analyses. In Experiment 2, an independent group of native English listeners sorted the group of 17 languages in terms of their distance from English. Experiment 3 repeated Experiment 2 with four groups of non-native English listeners: Dutch, Mandarin, Turkish and Korean listeners. Taken together, the results of these three experiments represent a step towards establishing an approach to assess the overall phonetic similarity of languages. This approach could potentially provide the basis for developing predictions regarding foreign-accented speech intelligibility for various listener groups, and regarding speech perception accuracy in the context of background noise in various languages.

This article examines how probability (lexical frequency and previous mention), speech style, and prosody affect word duration, and how these factors interact. Participants read controlled materials in clear and plain speech styles. As expected, more probable words (higher frequencies and clear speech second mentions) were significantly shorter than less probable words, and lexical frequency words in plain speech were significantly shorter than those in clear speech. Interestingly, we found second mention reduction effects in both clear and second mention plain speech, indicating that while clear speech is hyper-articulated, this reduction hyper-articulation does not override probabilistic effects on duration. We also found an interaction between mention and frequency, but only in plain speech. High frequency words allowed more second mention reduction than low frequency words in plain speech, revealing a tendency to hypo-articulate as much as possible when all factors support it. Finally, we found that first mentions were more likely to be accented than second mentions. However, when these differences in accent likelihood were controlled, a significant second mention reduction effect remained. This supports the concept of a direct link between probability and duration, rather than a relationship solely mediated by prosodic prominence.

Most second language acquisition research focuses on linguistic structures, and less research has examined the acquisition of sociolinguistic patterns. The current study explored the perceptual classification of regional dialects of American English by native and non-native listeners using a free classification task. Results revealed similar classification strategies for the native and non-native listeners. However, the native listeners were more accurate overall than the non-native listeners. In addition, the non-native listeners were less able to make use of constellations of cues to accurately classify the talkers by dialect. However, the non-native listeners were able to attend to cues that were either phonologically or sociolinguistically relevant in their native language. These results suggest that non-native listeners can use information in the speech signal to classify talkers by regional dialect, but that their lack of signal-independent cultural knowledge about variation in the second language leads to less accurate classification performance.

This article provides an overview of the research concerning the nature of the distinct, listener-oriented speaking style called ‘clear speech’ and its effect on intelligibility for various listener populations. We review major findings that identify talker, listener and signal characteristics that contribute to the characteristically high intelligibility of clear speech. Understanding the interplay of these factors sheds light on the interaction between higher level cognitive and lower-level sensory and perceptual factors that affect language processing. Clear speech research is, thus, relevant for both its theoretical insights and practical applications. Throughout the review, we highlight open questions and promising future directions.

Objective The purpose of this study is to expand our understanding of how the human auditory brainstem encodes temporal and spectral acoustic cues in voiced stop consonant–vowel syllables. Methods Auditory evoked potentials measuring activity from the brainstem of 22 normal learning children were recorded to the voiced stop consonant syllables [ga], [da], and [ba]. Spectrotemporal information distinguishing these voiced consonant–vowel syllables is contained within the first few milliseconds of the burst and the formant transition to the vowel. Responses were compared across stimuli with respect to their temporal and spectral content. Results Brainstem response latencies change in a predictable manner in response to systematic alterations in a speech syllable indicating that the distinguishing acoustic cues are represented by neural response timing (synchrony). Spectral analyses of the responses show frequency distribution differences across stimuli (some of which appear to represent acoustic characteristics created by difference tones of the stimulus formants) indicating that neural phase-locking is also important for encoding these acoustic elements. Conclusions Considered within the context of existing knowledge of brainstem encoding of speech–sound structure, these data are the beginning of a comprehensive delineation of how the human auditory brainstem encodes perceptually critical features of speech. Significance The results of this study could be used to determine how neural encoding is disrupted in the clinical populations for whom stop consonants pose particular perceptual challenges (e.g., hearing impaired individuals and poor readers).

This study investigated the effect of hyperarticulated, intelligibility-enhancing clear speech on temporal characteristics as reflected in number, durations, and variability of consonant and vowel intervals in sentence- and paragraph-length utterances. The results of sentence-in-noise listening tests showed a consistent clear speech intelligibility gain across the utterances of varying complexity indicating that the talkers successfully maintained clear speech articulatory modifications throughout longer stretches of speech. The acoustic analysis revealed that some temporal restructuring accompanied changes in speaking style. This temporal restructuring was observed in the insertion of consonant and vowel segments that were dropped or coarticulated in conversational speech and in an increase in the number of prosodic phrases for clear speech. Importantly, coefficients of variation (variation of consonantal and vocalic intervals normalized for changes in speaking rate) for both consonantal and vowel intervals remained stable in the two speaking styles. Overall, these results suggest that increased intelligibility of clear speech may be attributed to prosodic structure enhancement (increased phrasing and enhanced segmentability) and stable global temporal properties.

This study investigated the intelligibility of native and Mandarin-accented English speech for native English and native Mandarin listeners. The word-final voicing contrast was considered (as in minimal pairs such as `cub' and `cup') in a forced-choice word identification task. For these particular talkers and listeners, there was evidence of an interlanguage speech intelligibility benefit for listeners (i.e., native Mandarin listeners were more accurate than native English listeners at identifying Mandarin-accented English words). However, there was no evidence of an interlanguage speech intelligibility benefit for talkers (i.e., native Mandarin listeners did not find Mandarin-accented English speech more intelligible than native English speech). When listener and talker phonological proficiency (operationalized as accentedness) was taken into account, it was found that the interlanguage speech intelligibility benefit for listeners held only for the low phonological proficiency listeners and low phonological proficiency speech. The intelligibility data were also considered in relation to various temporal-acoustic properties of native English and Mandarin-accented English speech in effort to better understand the properties of speech that may contribute to the interlanguage speech intelligibility benefit.

Objective Deficient prosody is a hallmark of the pragmatic (socially contextualized) language impairment in Autism Spectrum Disorders (ASD). Prosody communicates emotion and intention and is conveyed through acoustic cues such as pitch contour. Thus, the objective of this study was to examine the subcortical representations of prosodic speech in children with ASD. Methods Using passively evoked brainstem responses to speech syllables with descending and ascending pitch contours, we examined sensory encoding of pitch in children with ASD who had normal intelligence and hearing and were age-matched with typically developing (TD) control children. Results We found that some children on the autism spectrum show deficient pitch tracking (evidenced by increased Frequency and Slope Errors and reduced phase locking) compared with TD children. Conclusions This is the first demonstration of subcortical involvement in prosody encoding deficits in this population of children. Significance Our findings may have implications for diagnostic and remediation strategies in a subset of children with ASD and open up an avenue for future investigations.

This study investigated talker-dependent and talker-independent perceptual adaptation to foreign-accent English. Experiment 1 investigated talker-dependent adaptation by comparing native English listeners' recognition accuracy for Chinese-accented English across single and multiple talker presentation conditions. Results showed that the native listeners adapted to the foreign-accented speech over the course of the single talker presentation condition with some variation in the rate and extent of this adaptation depending on the baseline sentence intelligibility of the foreign-accented talker. Experiment 2 investigated talker-independent perceptual adaptation to Chinese-accented English by exposing native English listeners to Chinese-accented English and then testing their perception of English produced by a novel Chinese-accented talker. Results showed that, if exposed to multiple talkers of Chinese-accented English during training, native English listeners could achieve talker-independent adaptation to Chinese-accented English. Taken together, these findings provide evidence for highly flexible speech perception processes that can adapt to speech that deviates substantially from the pronunciation norms in the native talker community along multiple acoustic-phonetic dimensions.

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.

When instructed to speak clearly for people with hearing loss, a talker can effectively enhance the intelligibility of his/her speech by producing "clear" speech. We analyzed global acoustic properties of clear and conversational speech from two talkers and measured their speech intelligibility over a wide range of signal-to-noise ratios in acoustic and electric hearing. Consistent with previous studies, we found that clear speech had a slower overall rate, higher temporal amplitude modulations, and also produced higher intelligibility than conversational speech. To delineate the role of temporal amplitude modulations in clear speech, we extracted the temporal envelope from a number of frequency bands and replaced speech fine-structure with noise fine-structure to simulate cochlear implants. Although both simulated and actual cochlear-implant listeners required higher signal-to-noise ratios to achieve normal performance, a 3-4 dB difference in speech reception threshold was preserved between clear and conversational speech for all experimental conditions. These results suggest that while temporal fine structure is important for speech recognition in noise in general, the temporal envelope carries acoustic cues that contribute to the clear speech intelligibility advantage.

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.

This study examined whether language specific properties may lead to cross-language differences in the degree of phonetic reduction. Rates of syllabic reduction (defined here as reduction in which the number of syllables pronounced is less than expected based on canonical form) in English and Mandarin were compared. The rate of syllabic reduction was higher in Mandarin than English. Regardless of language, open syllables participated in reduction more often than closed syllables. The prevalence of open syllables was higher in Mandarin than English, and this phonotactic difference could account for Mandarin's higher rate of syllabic reduction.

In order to investigate the precise acoustic features of stop consonants that pose perceptual difficulties for some children with learning problems, discrimination thresholds along two separate synthetic /da-ga/ continua were compared in a group of children with learning problems (LP) and a group of normal children. The continua differed only in the duration of the formant transitions. Results showed that simply lengthening the formant transition duration from 40 to 80 ms did not result in improved discrimination thresholds for the LP group relative to the normal group. Consistent with previous findings, an electrophysiologic response that is known to reflect the brain's representation of a change from one auditory stimulus to another--the mismatch negativity (MMN)--indicated diminished responses in the LP group relative to the normal group to /da/ versus /ga/ when the transition duration was 40 ms. In the lengthened transition duration condition the MMN responses from the LP group were more similar to those from the normal group, and were enhanced relative to the short transition duration condition. These data suggest that extending the duration of the critical portion of the acoustic stimulus can result in enhanced encoding at a preattentive neural level; however, this stimulus manipulation on its own is not a sufficient acoustic enhancement to facilitate increased perceptual discrimination of this place-of-articulation contrast.

In order to gain insight into the interplay between the talker-, listener-, and item-related factors that influence speech perception, a large multi-talker database of digitally recorded spoken words was developed, and was then submitted to intelligibility tests with multiple listeners. Ten talkers produced two lists of words at three speaking rates. One list contained lexically "easy" words (words with few phonetically similar sounding "neighbors" with which they could be confused), and the other list contained lexically "hard" words (words with many phonetically similar sounding "neighbors"). An analysis of the intelligibility data obtained with native speakers of English (experiment 1) showed a strong effect of lexical similarity. Easy words had higher intelligibility scores than hard words. A strong effect of speaking rate was also found whereby slow and medium rate words had higher intelligibility scores than fast rate words. Finally, a relationship was also observed between the various stimulus factors whereby the perceptual difficulties imposed by one factor, such as a hard word spoken at a fast rate, could be overcome by the advantage gained through the listener's experience and familiarity with the speech of a particular talker. In experiment 2, the investigation was extended to another listener population, namely, non-native listeners. Results showed that the ability to take advantage of surface phonetic information, such as a consistent talker across items, is a perceptual skill that transfers easily from first to second language perception. However, non-native listeners had particular difficulty with lexically hard words even when familiarity with the items was controlled, suggesting that non-native word recognition may be compromised when fine phonetic discrimination at the segmental level is required. Taken together, the results of this study provide insight into the signal-dependent and signal-independent factors that influence spoken language processing in native and non-native listeners.

This review paper describes an “acoustic-phonetic” experimental approach aimed at understanding normal and abnormal speech perception processes from both a behavioral and an electrophysiologic perspective. First, we consider the relevant acoustic characteristics of speech and identify a set of acoustic-phonetic classes that represent the parameters most important for making an acoustic signal sound like speech. Second, we review what is known about the neurophysiologic representation of acoustic-phonetic speech parameters in animal and human subjects. Third, we describe how an acoustic-phonetic approach has been useful in understanding the biologic basis of some auditory learning problems in children and in characterizing the behavioral and neurophysiologic changes resulting from speech-sound training. Finally, we discuss these findings and how they may expand the diagnostic and rehabilitative repertoire of practicing audiologists. Abbreviations: F0 = fundamental frequency; F1, F2, etc. = first formant, second formant, etc; fMRI = functional magnetic resonance imaging; JND = just noticeable difference; MMN = mismatch negativity

Two experiments were run to investigate language-specific and universal acoustic-perceptual characteristics of the /i/–/e/ and /u/–/o/ contrasts in two languages that differ widely in the sizes of their vowel inventories, namely, English and Spanish. In order to investigate the relationship between production and perception of these two vowel pairs, the first experiment compared the acoustic and perceptual characteristics of the /i/–/e/ and /u/–/o/ contrasts within each of the two languages. In order to investigate the responses of listeners to non-native stimuli, the second experiment presented native listeners of English and Spanish with synthetic /i/–/e/ and /u/–/o/ stimuli that were modeled after natural vowels as spoken by speakers of the other language. The results indicated a close production-perception link, as well as a degree of flexibility of the perceptual vowel space in response to stimuli that are structured around non-native vowel category locations. These results suggest that listeners perceive vowel stimuli with reference to a specific phonemic vowel system, and, if necessary, will adjust their perceptual vowel system to match the stimuli. Additionally, a comparison of the absolute locations of the /i/–/e/ and /u/–/o/ perceptual boundaries across the two languages indicated the presence of universally preferred, inventory-independent boundary locations.

Purpose It is established that speaking clearly is an effective means of enhancing intelligibility. Because any signal-processing scheme modeled after known acoustic–phonetic features of clear speech will likely affect both target and competing speech, it is important to understand how speech recognition is affected when a competing speech signal is also spoken clearly. In 2 experiments, the authors investigated whether listeners would experience improved intelligibility when both target and nontarget speech were spoken clearly. Method Listeners' recognition of sentences in competing sounds was examined in 2 experiments. For both experiments, the target speech was spoken in conversational and clear styles. The competing sounds in Experiment 1 included 2-talker maskers spoken in conversational and clear styles of English or Croatian. The competing sounds in Experiment 2 included 1-talker maskers spoken in clear or conversational styles and temporally modulated white noise maskers shaped to mimic the 1-talker maskers. Results Performance increased for clear versus conversational targets. No significant differences were found between conversational and clear maskers. Conclusions If it were possible to implement clear speech through a listening device, it appears that listeners would still receive a clear-speech benefit, even if all sounds (including competing sounds) were (inadvertently) processed to be more clear.

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.

Vowel production in gay, lesbian, bisexual (GLB), and heterosexual speakers was examined. Differences in the acoustic characteristics of vowels were found as a function of sexual orientation. Lesbian and bisexual women produced less fronted /u/ and /ɑ/ than heterosexual women. Gay men produced a more expanded vowel space than heterosexual men. However, the vowels of GLB speakers were not generally shifted toward vowel patterns typical of the opposite sex. These results are inconsistent with the conjecture that innate biological factors have a broadly feminizing influence on the speech of gay men and a broadly masculinizing influence on the speech of lesbian/bisexual women. They are consistent with the idea that innate biological factors influence GLB speech patterns indirectly by causing selective adoption of certain speech patterns characteristic of the opposite sex.

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.

Languages differ widely in the size of their vowel inventories; however, cross‐linguistic surveys indicate that certain vowels and vowel system configurations are preferred. A cross‐linguistic comparison of the acoustic vowel categories of two languages that differ in vowel inventory size, namely, English and Spanish, was performed in order to reveal some of the language‐specific and/or universal principles that determine the acoustic realization of the vowels of these two languages. This comparison shows that the precise location in the acoustic space of similar vowel categories across the two languages is determined, in part, by a language‐specific base‐of‐articulation property. These data also suggest that the relatively crowded acoustic vowel space of English may be expanded with respect to the relatively uncrowded acoustic vowel space of Spanish; however, this effect is variable depending on the syllable context of the English vowels. Finally, the data indicate no difference in the tightness of within‐category clustering for the large versus the small vowel inventory.

This study investigated the relationship between performance in perception and production, and the relationship between degrees of learning in the two domains within individual subjects. Eleven monolingual Japanese adults participated in an /r/–/l/ perceptual training program. Both perception data (minimal pair identification scores) and production data (recordings of /r/–/l/ minimal pair productions) were collected before and after perceptual training. Pre‐ and post‐test production data were then evaluated by native speakers of American English in a minimal pair identification task. Results showed considerable individual variation in all aspects of the perception–production relationship. Subjects varied widely in pretest levels of performance in both perception and production, as well as in improvement in perception and production. In general, subjects who performed well in the perception pretest also had good productions at pretest; however, subjects who were low performers in the perception pretest varied in their production abilities at pretest. Additionally, there was considerable variation in the transfer of perceptual learning to production. Subjects with a relatively high degree of improvement in perception did not necessarily have a comparable degree of improvement in production. Possible sources of these individual differences, and implications for the perception–production link will be discussed.

This paper presents the results of a pilot experiment for a larger study of the effect of inventory size and structure on vowel production and perception. This study will use acoustic and perceptual data from languages which vary in the size and structure of their vowel inventories to address questions regarding the connection between vowel production and perception, and regarding the universality of language specificity of vowel space categorizations. The data for this pilot study are from four speakers of each of two languages (English and Spanish), which differ in the size of their vowel inventories: English has 11 distinct vowel qualities whereas Spanish has 5. For the production study, recordings of words which illustrate the vowel contrasts were digitized and the formant frequencies of the target vowel steady states were measured from LPC spectra. The resultant vowel charts were plotted using various scales (koenig, mel, bark, log frequency), which were then compared in terms of their efficiency in ...

Even within careful speaking conditions, normal speakers vary in intelligibility. This study investigated vowel space characteristics as one correlate of variation in intelligibility. Data consisted of 100 Harvard sentences, spoken by 20 speakers and transcribed by ten listeners per speaker. Formant measurements (mel transformed) of six tokens each for three vowels [i,a,o] provided a basis for assessing the vowel‐space characteristics. First, vowel‐space area was calculated as the Euclidean area between vowel category means. Across all 20 speakers, this area did not correlate with intelligibility. However, for a subset of the speakers (three highest, three lowest in intelligibility) there was a moderate positive correlation (r=+0.34). Second, vowel‐space dispersion was calculated as the mean distance from the center of the triangular space to all 18 tokens. This dispersion measure showed a moderate, positive correlation with intelligibility across all 20 speakers (r=+0.43), suggesting the importance of individual token location for overall intelligibility. Finally, minimum and maximum formant values gave a measure of F1 and F2 range covered by vowel tokens. This measure revealed that F1 range correlated positively with intelligibility (r=+0.53), whereas F2 range did not. The results will be discussed in the context of talker variability and intelligibility.

Previous research has shown a significant correlation between the perception and production of English /r/ and /l/ by Japanese speakers [Yamada et al., Proc. ICSLP94, 2023–2026 (1994)]. The present study further investigated this perception‐production link by examining the transfer of training in perception to production of a non‐native contrast. Twelve monolingual Japanese speakers were trained to perceive the English /r/–/l/ contrast using a high‐variability training program [Lively et al., 2076–2087]. Recordings were also made of the trainees’ productions of English /r/‐/l/ minimal pairs before and after the perceptual training. These pretest and post‐test recordings were then evaluated perceptually by American listeners who were presented with pairs of tokens in an A‐B test format. As expected, subjects’ accuracy on the perceptual task improved by about 16% after 45 training sessions. More importantly, subjects’ productions at pretest and at post‐test were distinguishable by American listeners. More p...

In contrast to results of training with stimuli produced by 5 talkers, Lively et al. [ 1242–1255 (1993)] reported that Japanese adults trained to perceive English /r/ and /l/ with stimuli produced by a single talker failed to improve from pretest to post‐test, or to generalize to novel stimuli. That study was extended by training 5 groups of subjects each with a different talker, and by examining the retention of learning after 3 and 6 months. The previous results were partially replicated: Although all subjects showed significant learning during training, subjects in 3 of the 5 groups did not show significant improvement in a pretest–post‐test comparison, did not generalize well to new stimuli, and did not show good retention in 3‐ and 6‐month follow‐up tests. Subjects in two of the five groups improved significantly from pretest to post‐test, generalized well to new stimuli, and showed retention comparable to that of subjects trained with multiple talkers. The results indicate that while multiple‐talker training leads to consistently good results, training with stimuli produced by only one talker may fail to promote generalization to new stimuli and talkers under certain conditions.

Intelligibility tests of a database of 2000 recorded sentences (100 sentences produced by 20 talkers), show considerable variation in intelligibility across both sentences and talkers. This paper presents preliminary results of a study designed to identify the lexical and talker characteristics that correlate with speech intelligibility scores. To identify sentence‐specific correlates of intelligibility, lexical characteristics of the words that comprise the most versus the least intelligible sentences were compared. Results show that high‐intelligibility sentences have a higher proportion of function to content words, and consequently, a higher mean word frequency than low‐intelligibility sentences. Furthermore, lexical characteristics of the most common word‐level substitution errors indicate the importance of word frequency in overall sentence intelligibility. To identify talker‐specific correlates of intelligibility, acoustic measurements of sentences that show the most inter‐speaker variability in intelligibility were compared. For example, durational characteristics of the most common segment‐level errors indicated that the relative timing between segments is an important aspect of talker intelligibility. Future directions and general implications of this database project will be discussed. [Work supported by NIH Training Grant No. T32 DC‐00012 and NIH Research Grant No. R01 DC‐00111.]

This paper addresses three issues. First, the effect of inventory size on the acoustic realization of vowels in English and Spanish is examined. Results indicate that the English vowel space differs from the Spanish vowel space in range, but not in tightness of within‐category clustering. The second experiment tests the hypothesis that the perceptual categories coincide with the produced categories within a given language. Indeed, the data suggest that the perceptual and acoustic vowel spaces within English and Spanish correspond closely to each other. Finally, this study explores cross‐language differences in vowel perception. These data suggest that there are universal, perhaps psychophysical, boundaries which are independent of inventory size: in both languages, the boundaries between /i/ and /e/, and between /u/ and /o/ are primarily in the F1 dimension, and are in the 400‐ to 500‐mels region. This suggests that the observed regularities in vowel inventories across languages may stem, in part, from universal, auditory‐perceptual mechanisms. Results of experiments in which English listeners responded to Spanish‐based stimuli, and vice‐versa, will also be discussed.

This paper reports on three experiments [J. Ohala and D. Feder, J. Acoust. Soc. Am. Suppl. 1 80, S110 (1986)], designed to show that inferencing occurs commonly in speech perception. This challenges the direct‐realist theory [C. A. Fowler, J. Phon. 14, 3–28 (1986)] that claims that speech perception is direct, and not mediated by any cognitive processes. A preliminary experiment showed that the category boundary between [i] and [u] shifts toward [u] next to a bilabial C, and toward [i] next to an alveolar. This boundary shift recurs in V1CV2 stimuli in which the C was masked by white noise. (V1 varies between [i] and [u]; V2 is always [a].) These masked stimuli were presented in blocks where the medial C was always either [b] or [d], which allowed the masked consonant to be “restored” based on the audible consonant in the unmasked stimuli. In the second experiment, 80% of the stimuli in each block had either [b] or [d], and the remaining 20% had the contrasting place. In the third experiment, the 20% minority contained [g]'s. In both cases, the vowel category boundary should exhibit an effect of the place of the 80% “context” stimuli. With [b] or [d], the place of the 20% minority should also effect the [i]‐[u] boundary, but [g] should not shift the boundary because listeners would expect [g], unlike [b] and [d], to vary with vowel backness. Preliminary analyses indicate thai expectation participates jointly with direct acoustic analysis in speech perception.