Acoustic Salience Research Articles

The articulatory and acoustic characteristics of Polish sibilants and their consequences for diachronic change

The study is concerned with the relative synchronic stability of three contrastive sibilant fricatives /sʂ ɕ/ in Polish. Tongue movement data were collected from nine first-language Polish speakers producing symmetrical real and non-word CVCV sequences in three vowel contexts. A Gaussian model was used to classify the sibilants from spectral information in the noise and from formant frequencies at vowel onset. The physiological analysis showed an almost complete separation between /sʂ ɕ/ on tongue-tip parameters. The acoustic analysis showed that the greater energy at higher frequencies distinguished /s/ in the fricative noise from the other two sibilant categories. The most salient information at vowel onset was for /ɕ/, which also had a strong palatalizing effect on the following vowel. Whereas either the noise or vowel onset was largely sufficient for the identification of /sɕ/ respectively, both sets of cues were necessary to separate /ʂ/ from /sɕ/. The greater synchronic instability of /ʂ/ may derive from its high articulatory complexity coupled with its comparatively low acoustic salience. The data also suggest that the relatively late stage of /ʂ/ acquisition by children may come about because of the weak acoustic information in the vowel for its distinction from /s/.

Perception of tones by bilingual infants learning non-tone languages

This paper examines the ability of bilingual infants who were learning Dutch and another non-tone language to discriminate tonal contrasts. All infants from 5 to 18 months of age succeeded in discriminating a tonal contrast of Mandarin Chinese (Tone 1 versus Tone 4) and showed a U-shaped pattern when facing a less acoustically salient manipulated version (contracted) of the aforementioned contrast. Specifically, infants showed initial sensitivity to the contracted contrast during their early months, followed by a loss of sensitivity at the stage where tonal perceptual reorganization typically occurs, and a sensitivity rebound by the end of the first year after birth. Compared to a previous studying of ours testing monolingual Dutch infants (Liu & Kager, 2014), the discrimination patterns of bilingual infants revealed both similarities and differences. On one hand, as with monolinguals, non-tone-learning bilingual infants’ tonal perception presented plasticity influenced by contrast acoustic salience along the trajectory of perceptual reorganization; as well as a general U-shaped perceptual pattern when discriminating non-native tones. On the other hand, bilingual infants appeared to regain sensitivity to the contracted tonal contrast at an earlier age (11–12 months) in comparison with monolinguals infants (17–18 months). We provide several explanations, stemming from the simultaneous exposure to two languages, to account for the 6-month bilingual perceptual plasticity from linguistic and cognitive perspectives. The overall outcomes of the study offer insights into the infant perceptual reorganization and language development trajectory, expand on the differences between monolingual and bilingual language development, and broaden our understanding of the influence of bilingual exposure to the perception of non-native contrasts in infancy from linguistic and cognitive perspectives.

Rapid learning of minimally different words in five- to six-year-old children: effects of acoustic salience and hearing impairment.

This study investigates the role of acoustic salience and hearing impairment in learning phonologically minimal pairs. Picture-matching and object-matching tasks were used to investigate the learning of consonant and vowel minimal pairs in five- to six-year-old deaf children with a cochlear implant (CI), and children of the same age with normal hearing (NH). In both tasks, the CI children showed clear difficulties with learning minimal pairs. The NH children also showed some difficulties, however, particularly in the picture-matching task. Vowel minimal pairs were learned more successfully than consonant minimal pairs, particularly in the object-matching task. These results suggest that the ability to encode phonetic detail in novel words is not fully developed at age six and is affected by task demands and acoustic salience. CI children experience persistent difficulties with accurately mapping sound contrasts to novel meanings, but seem to benefit from the relative acoustic salience of vowel sounds.

The acoustic salience of prosody trumps infants' acquired knowledge of language-specific prosodic patterns.

There is mounting evidence that prosody facilitates grouping the speech stream into syntactically-relevant units (e.g., Hawthorne & Gerken, 2014; Soderstrom, Kemler Nelson, & Jusczyk, 2005). We ask whether prosody's role in syntax acquisition relates to its general acoustic salience or to the learner's acquired knowledge of correlations between prosody and syntax in her native language. English- and Japanese-acquiring 19-month-olds listened to sentences from an artificial grammar with non-native prosody (Japanese or English, respectively), then were tested on their ability to recognize prosodically-marked constituents when the constituents had moved to a new position in the sentence. Both groups were able to use non-native prosody to parse speech into cohesive, reorderable, syntactic constituent-like units. Comparison with Hawthorne & Gerken (2014), in which English-acquiring infants were tested on sentences with English prosody, suggests that 19-month-olds are equally adept at using native and non-native prosody for at least some types of learning tasks and, therefore, that prosody is useful in early syntactic segmentation because of its acoustic salience.

Phonological and morphophonological effects on grammatical development in children with specific language impairment.

Five-year-olds with specific language impairment (SLI) often struggle with mastering grammatical morphemes. It has been proposed that verbal morphology is particularly problematic in this respect. Previous research has also shown that in young typically developing children grammatical markers appear later in more phonologically challenging contexts. The main aim was to explore whether grammatical deficits in children with SLI are morphosyntactic in nature, or whether phonological factors also explain some of the variability in morpheme production. The analysis considered the effects of the same phonological factors on the production of three different morphemes: two verbal (past tense -ed; third-person singular -s) and one nominal morpheme (possessive -s). The participants were 30 children with SLI (21 boys) aged 4;6-5;11 years (mean = 5;1). The data were collected during grammar test sessions, which consisted of question/answer elicitations of target forms involving picture props. A total of 2301 items were analysed using binary logistic regression; the predictors included: (1) utterance position of the target word, (2) phonological complexity of its coda, (3) voicing of the final stem consonant, (4) syllabicity (allomorph type) and (5) participant accounting for the individual differences in the responses. The results showed a robust effect of syllabicity on the correct morpheme production. Specifically, syllabic allomorphs (e.g., She dresses) were significantly more challenging than the segmental ones (e.g., He runs) for all three morphemes. The effects of other factors were observed only for a single morpheme: coda complexity and voicing helped explain variability in past tense production, and utterance position significantly affected children's performance with the possessive. The participant factor also had a significant effect, indicating high within-group variability--often observed in SLI population. The systematic effect of syllabicity across both verbal and nominal morphemes suggests morphophonological influences in the grammatical development of children with SLI that cannot be fully explained by syntactic deficits. Poorer performance in producing syllabic allomorphs can be accounted for by much lower overall frequency of these forms, and by the 'tongue-twisting' effect of producing similar segments in succession, as in added [aedəd], washes [wɒʃəz]. Interestingly, the greater acoustic salience of the syllabic allomorphs (an extra syllable) does not enhance children's abilities to produce them. These findings suggest that the interconnections between different levels of language have a stronger effect on the grammatical development of children with SLI than might be expected. Allomorphy should, therefore, be taken into account when designing language assessments and speech therapy, ensuring that children receive sufficient practice with the entire set of allomorphic variants.

Perception of tones by infants learning a non-tone language

This article examines the perception of tones by non-tone-language-learning (non-tone-learning) infants between 5 and 18months in a study that reveals infants’ initial sensitivity to tonal contrasts, deterioration yet plasticity of tonal sensitivity at the end of the first year, and a perceptual rebound in the second year. Dutch infants in five age groups were tested on their ability to discriminate a tonal contrast of Mandarin Chinese as well as a contracted tonal contrast. Infants are able to discriminate tonal contrasts at 5–6months, and their tonal sensitivity deteriorates at around 9months. However, the sensitivity rebound sat 17–18months. Non-tone-learning infants’ tonal perception is elastic, as is shown by the influence of acoustic salience and distributional learning: (1) a salient contrast may remain discriminable throughout infancy whereas a less salient one does not; (2) a bimodal distribution in tonal exposure increases non-tone-learning infants’ discrimination ability during the trough in sensitivity to tonal contrasts at 11–12months. These novel findings reveal non-tone-learning infants’ U-shaped pattern in tone perception, and display their perceptual flexibility.

Task-dependent neural representations of salient events in dynamic auditory scenes.

Selecting pertinent events in the cacophony of sounds that impinge on our ears every day is regulated by the acoustic salience of sounds in the scene as well as their behavioral relevance as dictated by top-down task-dependent demands. The current study aims to explore the neural signature of both facets of attention, as well as their possible interactions in the context of auditory scenes. Using a paradigm with dynamic auditory streams with occasional salient events, we recorded neurophysiological responses of human listeners using EEG while manipulating the subjects' attentional state as well as the presence or absence of a competing auditory stream. Our results showed that salient events caused an increase in the auditory steady-state response (ASSR) irrespective of attentional state or complexity of the scene. Such increase supplemented ASSR increases due to task-driven attention. Salient events also evoked a strong N1 peak in the ERP response when listeners were attending to the target sound stream, accompanied by an MMN-like component in some cases and changes in the P1 and P300 components under all listening conditions. Overall, bottom-up attention induced by a salient change in the auditory stream appears to mostly modulate the amplitude of the steady-state response and certain event-related potentials to salient sound events; though this modulation is affected by top-down attentional processes and the prominence of these events in the auditory scene as well.

On the importance of being noticed: the role of acoustic salience in phonotactics (and casual speech)

In the very rich literature on phonotactics, the role of acoustic salience has sometimes been hinted but the topic has never been investigated in depth. In this paper, it is shown that factors like markedness, sonority and the Net Auditory Distance (a concept used in the Beats-and-Binding phonology framework) are not able to explain exhaustively certain phonotactic phenomena. I therefore attempt to bring experimental evidence that the role of salience is apparent in the perception of plateau clusters, i.e., obstruent clusters, nasal clusters and liquid clusters. The hypothesis is that the more salient a consonant, the more easily it will be perceived correctly as the first member of an initial plateau cluster and as the last member of a final plateau cluster. A salience scale is devised based on data from Italian and Dutch casual speech reductions, attested plateau clusters in the world's languages and former experimental studies. The results of the experiment, which presented nonce words containing plateau clusters as stimuli to Italian and Dutch native speakers, confirm the initial hypothesis for nasal and liquid clusters but only partially for obstruent clusters. It is suggested that the proposed salience scale has to be reformulated and that factors other than salience have to be taken into account.

Auditory Training: Evidence for Neural Plasticity in Older Adults.

Improvements in digital amplification, cochlear implants, and other innovations have extended the potential for improving hearing function; yet, there remains a need for further hearing improvement in challenging listening situations, such as when trying to understand speech in noise or when listening to music. Here, we review evidence from animal and human models of plasticity in the brain's ability to process speech and other meaningful stimuli. We considered studies targeting populations of younger through older adults, emphasizing studies that have employed randomized controlled designs and have made connections between neural and behavioral changes. Overall results indicate that the brain remains malleable through older adulthood, provided that treatment algorithms have been modified to allow for changes in learning with age. Improvements in speech-in-noise perception and cognition function accompany neural changes in auditory processing. The training-related improvements noted across studies support the need to consider auditory training strategies in the management of individuals who express concerns about hearing in difficult listening situations. Given evidence from studies engaging the brain's reward centers, future research should consider how these centers can be naturally activated during training.

Characterizing the morphosyntactic processing deficit and its relationship to phonology in developmental dyslexia

This study explores the morphosyntactic processing deficit in developmental dyslexia, addressing the on-going debate on the linguistic nature of the disorder, and directly testing the hypothesis that the deficit is based on underlying processing difficulties, such as acoustic and/or phonological impairments. Short German sentences consisting of a pronoun and a verb, either correct or containing a morphosyntactic violation, were auditorily presented to 17 German-speaking adults with dyslexia, and 17 matched control participants, while an EEG was recorded. In order to investigate the interaction between low-level phonological processing and morphosyntactic processing, the verbal inflections were manipulated to consist of different levels of acoustic salience. The event-related potential (ERP) results confirm altered morphosyntactic processing in participants with dyslexia, especially when morphosyntactic violations are expressed by both lexical and inflectional changes. Moreover, ERP data on phoneme discrimination and behavioural data on phonemic awareness and verbal short-term memory reveal phonological deficits in dyslexic participants. However, a causal relationship between phonological and morphosyntactic processing was not conclusive, because anomalous morphosyntactic processing in dyslexia is not directly mediated by acoustic salience, rather it correlates with high-level phonological skills and is mediated by lexical cues.

When does native language input affect phonetic perception? The precocious case of lexical tone

Previous studies have suggested that the perception of vowels and consonants changes from language-universal to language-specific between 6 and 12months of age. This report suggests that language-specific perception emerges even earlier for lexical tones. Experiment 1 tested English-learners’ perception of Cantonese tones, replicating declines in tone discrimination from 4 to 9months of age. Experiment 2 tested infants learning non-native versus native tone systems (Mandarin-learners versus Cantonese-learners). All Chinese-learners discriminated the tones, but showed language-specific differences in tone preferences at both ages. Indeed, English-, Mandarin-, and Cantonese-learning 4-month-olds all exhibited distinct preferences. With other work, this shows that language-specific speech perception emerges over a more complex and extended schedule than previously thought: first for lexical stress and tone (<5months), then vowels (6–8months), consonants (8.5–12months), and finally phoneme duration (18months). Acoustic salience likely plays an important role in determining the timing of phonetic development.

Event-related potentials to an english/spanish syllabic contrast in mexican 10-13-month-old infants.

We report brain electrophysiological responses from 10- to 13-month-old Mexican infants while listening to native and foreign CV-syllable contrasts differing in Voice Onset Time (VOT). All infants showed normal auditory event-related potential (ERP) components. Our analyses showed ERP evidence that Mexican infants are capable of discriminating their native sounds as well as the acoustically salient (aspiration) foreign contrast. The study showed that experience with native language influences VOT perception in Spanish learning infants. The acoustic salience of aspiration is perceived by both Spanish and English learning infants, but exposure provides additional phonetic status to this native-language feature for English learning infants. The effects of early experience and neural commitment as well as the impact of acoustic salience are further discussed.

Managing the distinctiveness of phonemic nasal vowels: Articulatory evidence from Hindi

There is increasing evidence that fine articulatory adjustments are made by speakers to reinforce and sometimes counteract the acoustic consequences of nasality. However, it is difficult to attribute the acoustic changes in nasal vowel spectra to either oral cavity configuration or to velopharyngeal opening (VPO). This paper takes the position that it is possible to disambiguate the effects of VPO and oropharyngeal configuration on the acoustic output of the vocal tract by studying the position and movement of the tongue and lips during the production of oral and nasal vowels. This paper uses simultaneously collected articulatory, acoustic, and nasal airflow data during the production of all oral and phonemically nasal vowels in Hindi (four speakers) to understand the consequences of the movements of oral articulators on the spectra of nasal vowels. For Hindi nasal vowels, the tongue body is generally lowered for back vowels, fronted for low vowels, and raised for front vowels (with respect to their oral congeners). These movements are generally supported by accompanying changes in the vowel spectra. In Hindi, the lowering of back nasal vowels may have originally served to enhance the acoustic salience of nasality, but has since engendered a nasal vowel chain shift.

The interaction between acoustic salience and language experience in developmental speech perception: evidence from nasal place discrimination

Previous research suggests that infant speech perception reorganizes in the first year: young infants discriminate both native and non-native phonetic contrasts, but by 10-12 months difficult non-native contrasts are less discriminable whereas performance improves on native contrasts. In the current study, four experiments tested the hypothesis that, in addition to the influence of native language experience, acoustic salience also affects the perceptual reorganization that takes place in infancy. Using a visual habituation paradigm, two nasal place distinctions that differ in relative acoustic salience, acoustically robust labial-alveolar [ma]-[na] and acoustically less salient alveolar-velar [na]-[ enga], were presented to infants in a cross-language design. English-learning infants at 6-8 and 10-12 months showed discrimination of the native and acoustically robust [ma]-[na] (Experiment 1), but not the non-native (in initial position) and acoustically less salient [na]-[ enga] (Experiment 2). Very young (4-5-month-old) English-learning infants tested on the same native and non-native contrasts also showed discrimination of only the [ma]-[na] distinction (Experiment 3). Filipino-learning infants, whose ambient language includes the syllable-initial alveolar (/n/)-velar (/ eng/) contrast, showed discrimination of native [na]-[ enga] at 10-12 months, but not at 6-8 months (Experiment 4). These results support the hypothesis that acoustic salience affects speech perception in infancy, with native language experience facilitating discrimination of an acoustically similar phonetic distinction [na]-[ enga]. We discuss the implications of this developmental profile for a comprehensive theory of speech perception in infancy.

Does prosodic constituency signal relative predictability? A Smooth Signal Redundancy hypothesis

AbstractThis paper explores issues relating to signaling word boundaries from the perspective of Aylett's Smooth Signal Redundancy proposal (Aylett, Stochastic suprasegmentals: Relationships between redundancy, prosodic structure and care of articulation in spontaneous speech, University of Edinburgh, 2000, Aylett and Turk, Language and Speech 47: 31–56, 2004) that language has evolved to spread redundancy, i.e. recognition likelihood, evenly throughout utterances. In Aylett's proposal, information that enables listeners to identify sequences of elements in an utterance (signal redundancy) comes from two sources: a) language redundancy, recognition likelihood based on lexical, syntactic, semantic, pragmatic and other factors, and b) acoustic redundancy, recognition likelihood based on acoustic salience. Smooth signal redundancy is achieved by a complementary relationship between language redundancy and acoustic redundancy that is implemented via prosodic structure.While Aylett and Turk (Language and Speech 47: 31–56, 2004) present the case for prosodic prominence as a lever for modulating the acoustic salience of syllables, the current paper proposes that prosodic constituency also fulfils this function for words. The current paper proposes that the signal redundancy, or recognition likelihood, of words can be manipulated by signaling their boundaries, and that the occurrence and strength of these boundary markers correlates inversely with language redundancy. Prosodic constituency implements the complementary relationship between language redundancy and word boundary salience.Smooth Signal Redundancy provides an integrated explanation for a set of properties relating to prosodic constituent structure.

Acquiring a new second language contrast: an analysis of the English laryngeal system of native speakers of Dutch

This study examines the acquisition of the English laryngeal system by native speakers of (Belgian) Dutch. Both languages have a two-way laryngeal system, but while Dutch contrasts prevoiced with short-lag stops, English has a contrast between short-lag and long-lag stops. The primary aim of the article is to test two hypotheses on the acquisition process based on first language acquisition research: (1) native speakers of a voicing language will succeed in producing short-lag stops in the target aspirating language, since short-lag stops occur early in first language acquisition and can be considered unmarked and since one member of the contrast is formed by short-lag stops in both voicing and aspirating languages, and (2) native speakers of a voicing language will succeed in acquiring long-lag stops in the target language, because aspiration is an acoustically salient realization. The analysis is based on an examination of natural speech data (conversations between dyads of informants), combined with the results of a controlled reading task. Both types of data were gathered in Dutch as well as in EngDutch (i.e. the English speech of native speakers of Dutch). The analysis revealed an interesting pattern: while the first language (L1) Dutch speakers were successful in acquiring long-lag aspirated stops (confirming hypothesis 2), they did not acquire English short-lag stops (rejecting hypothesis 1). Instead of the target short-lag stops, the L1 Dutch speakers produced prevoiced stops and frequently transferred regressive voice assimilation with voiced stops as triggers from Dutch into English. Various explanations for this pattern in terms of acoustic salience, perceptual cues and training will be considered.

Stability of temporal contrasts across speaking styles in English and Croatian

In this paper, we investigate the effect of clear speech, a distinct, listener-oriented, intelligibility-enhancing mode of speech production, on vowel and stop consonant contrasts along the temporal dimension in English and Croatian. Our previous work has shown that, in addition to enhancing the overall acoustic salience of the speech signal through a decrease in speaking rate and expansion of pitch range, clear speech modifications increased the spectral distances between vowel categories in both languages despite the different sizes of their vowel inventories (+10 in English, five in Croatian). Here, we examine how clear speech affects the duration of English tense (long) vs. lax (short) vowels, English vowels preceding voiced (long) vs. voiceless (short) coda stops, Croatian long vs. short vowels and Croatian and English voice onset time (VOT) duration for voiced and voiceless stops. Overall, the results showed that the proportional distance between the ‘short’ and ‘long’ vowel categories and between the voiced and voiceless stop categories was remarkably stable across the two speaking styles in both languages. These results suggest that, in combination with the spectral enhancement of vowel contrasts, language-specific pronunciation norms along the temporal dimension are maintained in clear and conversational speech.

Does attention play a role in dynamic receptive field adaptation to changing acoustic salience in A1?

Acoustic filter properties of A1 neurons can dynamically adapt to stimulus statistics, classical conditioning, instrumental learning and the changing auditory attentional focus. We have recently developed an experimental paradigm that allows us to view cortical receptive field plasticity on-line as the animal meets different behavioral challenges by attending to salient acoustic cues and changing its cortical filters to enhance performance. We propose that attention is the key trigger that initiates a cascade of events leading to the dynamic receptive field changes that we observe. In our paradigm, ferrets were initially trained, using conditioned avoidance training techniques, to discriminate between background noise stimuli (temporally orthogonal ripple combinations) and foreground tonal target stimuli. They learned to generalize the task for a wide variety of distinct background and foreground target stimuli. We recorded cortical activity in the awake behaving animal and computed on-line spectrotemporal receptive fields (STRFs) of single neurons in A1. We observed clear, predictable task-related changes in STRF shape while the animal performed spectral tasks (including single tone and multi-tone detection, and two-tone discrimination) with different tonal targets. A different set of task-related changes occurred when the animal performed temporal tasks (including gap detection and click-rate discrimination). Distinctive cortical STRF changes may constitute a “task-specific signature”. These spectral and temporal changes in cortical filters occur quite rapidly, within 2 min of task onset, and fade just as quickly after task completion, or in some cases, persisted for hours. The same cell could multiplex by differentially changing its receptive field in different task conditions. On-line dynamic task-related changes, as well as persistent plastic changes, were observed at a single-unit, multi-unit and population level. Auditory attention is likely to be pivotal in mediating these task-related changes since the magnitude of STRF changes correlated with behavioral performance on tasks with novel targets. Overall, these results suggest the presence of an attention-triggered plasticity algorithm in A1 that can swiftly change STRF shape by transforming receptive fields to enhance figure/ground separation, by using a contrast matched filter to filter out the background, while simultaneously enhancing the salient acoustic target in the foreground. These results favor the view of a nimble, dynamic, attentive and adaptive brain that can quickly reshape its sensory filter properties and sensori-motor links on a moment-to-moment basis, depending upon the current challenges the animal faces. In this review, we summarize our results in the context of a broader survey of the field of auditory attention, and then consider neuronal networks that could give rise to this phenomenon of attention-driven receptive field plasticity in A1.

Frenchville French: A case study in phonological attrition

This paper investigates the phonetic and phonological properties of a contracting variety of French spoken in Frenchville, PA, a linguistic enclave community. Specifically, we analyze a pattern of convergence versus preservation that cannot be convincingly explained or understood given current proposals of the process of phonological convergence and attrition in a bilingual contact situation. We demonstrate that our speakers preserve some low level information while sacrificing other phonetic details. In the case under investigation, there is a gradient replacement of the French mid front rounded vowels with an English-like rhoticized schwa but our speakers maintain language specific, phonetically distinct rhotic consonants. We argue that the patterns of loss versus maintenance that emerge are not necessarily driven by the need to preserve contrastive features with a high functional load. Equally plausible accounts for these patterns may lie in acoustic salience, the sociolinguistic marking of identity, and competition between articulatory demands.

Phonetic and phonological effects in production and perception of Croatian clear speech

This paper examines the interaction of language-general, signal enhancement strategies and language-specific, phonological enhancement strategies in clear speech production and perception in Croatian, a language with a phonemic vowel length contrast and a relatively small inventory of five vowel qualities. Two native speakers of Croatian (one male, one female) read 20 nonsense sentences in conversational and clear speech. In a sentence-in-noise perception test, native Croatian listeners more accurately recognized words produced in clear than in conversational speech by both talkers. However, this clear speech intelligibility benefit was greater for the male than the female talker. Acoustic analyses showed that in clear speech both talkers enhanced the overall acoustic salience of the signal (slower, more frequent pauses, wider pitch range) and expanded the vowel space, although the male showed slightly less extensive vowel space expansion. However, only the male talker enhanced the phonemic vowel length contrast, suggesting that the observed asymmetry in the clear speech intelligibility benefit between the talkers may be due to the contribution of this phonological enhancement feature of his (but not her) clear speech production. The results suggest that speech intelligibility is most effectively enhanced by acoustic-phonetic modifications that reflect a combination of acoustic-auditory and phonological factors.