Weighting Of Acoustic Cues Research Articles

Acoustic cue weighting in perception and production of English and Spanish

We present data quantifying the use of multiple acoustic dimensions in the perception and production of word-initial stops in Spanish and English in bilinguals and monolinguals, with a focus on the stability of individuals’ cue weighting strategies across languages and modalities. Early Spanish-English bilinguals who use both languages on a regular basis, along with control groups of monolingual Spanish and English speakers, categorized stop-initial CV syllables covarying in Voice Onset Time (VOT), fundamental frequency at vowel onset (f0), first formant onset frequency (F1), and stop closure duration. Individual perceptual cue weights were calculated via logistic regression, and these weights were compared with the same speakers’ use of the corresponding acoustic dimensions in their productions of the stop contrast. Preliminary results suggest that bilingual listeners’ perceptual cue weighting strategies correspond across Spanish and English; that is, individuals who weight a given cue more heavily than average in English also weight that cue heavily in Spanish. However, in line with previous work, correspondences between a given individual's use of the acoustic dimensions across perception and production are more elusive.

Discriminability and perceptual saliency of acoustic cues for final consonant voicing in simulations of cochlear-implant and electric-acoustic stimulation

Multiple redundant acoustic cues can contribute to the perception of a single class of speech sounds. This study investigates the effect of spectral degradation on the discriminability and perceptual saliency of acoustic cues for phonetic identification of word-final fricative voicing in “loss” versus “laws,” and possible changes that occur when low-frequency acoustic cues are restored. Three acoustic cues that contribute to the word-final /s/-/z/ contrast (first formant frequency [F1] offset, vowel-consonant duration ratio, and consonant voicing duration) were systematically varied in modified natural speech syllables. The first experiment measured listeners' ability to discriminate differences among stimuli within a single cue dimension. The second experiment examined the extent to which listeners make use of a given cue to label a syllable as “loss” versus “laws” when multiple cues are available. Normal-hearing listeners were presented with stimuli that were either unprocessed, processed with 8-channel noise-band vocoder to approximate CI spectral degradation, or low-pass (LP) filtered to simulate low-frequency residual hearing. They were tested in four listening conditions: unprocessed, vocoder alone, LP alone, and vocoder + LP where low-frequency fine-structure cues could enhance F1 perception and voicing cues. The impact of listening condition on discriminability and weighting of different acoustic cues will be discussed.

Cue weighting and vestibular mediation of temporal dynamics in sound localization via head rotation

Our studies have quantified the salience and weighting of dynamic acoustic cues in sound localization via head rotation. Results support three key findings: 1) low-frequency interaural time-difference (ITD) is the dominant dynamic binaural difference cue; 2) dynamic cues dominate front/rear localization only when spectral cues are unavailable; and 3) the temporal dynamics of dynamic cue processing are particular to auditory-vestibular integration. ITD dominance is shown indirectly in findings that head movements are highly effective for localizing low-frequency targets but not narrow-band high-frequency targets. Direct evidence comes from manipulation of dynamic binaural cues in spherical-head simulations lacking spectral cues. If the stimulus provides access to dominant high-frequency spectral cues, location illusions involving head-coupled source motion fail. For low-frequency targets, localization performance improves with increasing head-turn angle, but decreases with increasing velocity such that performance depends primarily on stimulus duration; ~100 ms being required for accurate front/back localization. That duration threshold only applies in dynamic localization tasks, and not in auditory-only tasks involving similar stimuli. Correct spatial interpretation of dynamic acoustic cues appears to require vestibular information about head motion, thus the temporal threshold is likely a property of vestibular-auditory integration.

Language experience modulates weighting of acoustic cues for vowel perception: An event‐related potential study

In behavioral tasks, previous research has found that advanced Spanish learners of Dutch rely on duration cues to distinguish Dutch vowels, while Dutch listeners rely on spectral cues. This study tested whether language-specific cue weighting is reflected in preattentive processing. The mismatch negativity (MMN) of Dutch and Spanish participants was examined in response to spectral and duration cues in Dutch vowels. The MMN at frontal and mid sites was weaker and peaked later at Fz for Spanish than for Dutch listeners for the spectrally cued contrasts, whereas both groups responded similarly to the duration cue. In line with overt categorization behavior, these MMN data indicate that preattentive cue weighting depends on the listeners' language experience.

Divergent patterns of voicing perception in various challenging listening conditions.

Perception of consonant voicing is especially robust, even under conditions of harsh spectral degradation, hearing loss, and background noise. Considering the limitations and variability of the acoustic input, it is unlikely that the same perceptual strategy is used in all situations. A sequence of experiments was designed to assess the weighting of multiple acoustic cues to the voicing contrast word‐initially and word‐finally, and to reveal patterns unavailable in conventional confusion matrices and information transfer analysis. In preliminary results, the combination of background noise and low‐pass filtering brought about a dramatic shift in weighting of the VOT and F0 cues for initial consonants; these degradations in isolation did not produce such a shift. Under conditions of spectral degradation (noise‐band vocoding), listeners significantly increased their use of vowel duration, and significantly decreased their use of vowel formant transition, which is dominant in the optimal condition. These results suggest that in challenging conditions, listeners are apt to use secondary acoustic cues that are potentially less reliable or less perceptually salient than primary cues used in optimal conditions. It is concluded that comparison of performances by listeners in various conditions should be guarded, even when recognition scores appear to be equivalent on the surface.

Do language-specific differences in primary acoustic cues affect relative weighting of secondary cues to phonological contrasts?

Cross-language differences in cue weighting are often attributed to differences in phonological inventories, in that listeners are assumed to give greater weight to those acoustic cues that best differentiate the specific phonological categories of their native language. However, subphonological properties of a given contrast may also affect weighting of acoustic cues for acoustic or perceptual reasons, in a manner independent of the structure of the listeners’ phonological inventory. Here, this possibility is investigated by comparing Spanish and English listeners’ relative weighting of two acoustic cues to the syllable-initial stop consonant voicing contrast /b/-/p/: Voice onset time (VOT) and fundamental frequency at the onset of voicing (onset f0). Spanish and English possess comparable word-initial stop consonant inventories, but differ in the phonetic realization of the voicing contrast in terms of VOT: Spanish contrasts a short lag (<10 ms) /p/ with a prevoiced (<0 ms) /b/, while English contrasts a long lag (> 50 ms) /p/ with a short lag (<20 ms) /b/. Preliminary results (N = 7) suggest that, although speakers from both languages depend mainly on VOT, Spanish speakers give more weight to onset f0 when VOT is ambiguous than do English listeners.

Listeners’ weighting of acoustic cues to synthetic speech naturalness: A multidimensional scaling analysis

The quality of current commercial speech synthesis systems is now so high that system improvements are being made at subtle sub- and supra-segmental levels. Human perceptual evaluation of such subtle improvements requires a highly sophisticated level of perceptual attention to specific acoustic characteristics or cues. However, it is not well understood what acoustic cues listeners attend to by default when asked to evaluate synthetic speech. It may, therefore, be potentially quite difficult to design an evaluation method that allows listeners to concentrate on only one dimension of the signal, while ignoring others that are perceptually more important to them. The aim of the current study was to determine which acoustic characteristics of unit-selection synthetic speech are most salient to listeners when evaluating the naturalness of such speech. This study made use of multidimensional scaling techniques to analyse listeners’ pairwise comparisons of synthetic speech sentences. Results indicate that listeners place a great deal of perceptual importance on the presence of artifacts and discontinuities in the speech, somewhat less importance on aspects of segmental quality, and very little importance on stress/intonation appropriateness. These relative differences in importance will impact on listeners’ ability to attend to these different acoustic characteristics of synthetic speech, and should therefore be taken into account when designing appropriate methods of synthetic speech evaluation.

On the relationship between the perception and learning of Hindi voicing and place contrasts by native speakers of American English.

Many non‐native speech sounds are challenging to perceive and, ultimately, to acquire. Predicting specific learning outcomes from perceptual data has been hampered by (1) problems in quantifying acoustic‐phonetic similarity between non‐native and native sounds, (2) calculating the perceptual weighting of acoustic cues in the native language, and (3) the high‐variability commonly observed in the perceptual assimilation of non‐native contrasts to multiple native categories. This variability may reflect long‐term persistent patterns in learning or it may represent only a brief early stage prior to fossilization. To examine these two possible accounts, the perceptual assimilation by 15 American English listeners of 7 voicing and place contrasts produced by 6 Hindi speakers was examined before and after training in a paired‐associate word learning task. Training utilized tokens from four of the six talkers used in perceptual assimilation tasks. The purpose of the study was to determine whether or not assimilat...

Cue-specific effects of categorization training on the relative weighting of acoustic cues to consonant voicing in English

In English, voiced and voiceless syllable-initial stop consonants differ in both fundamental frequency at the onset of voicing (onset F0) and voice onset time (VOT). Although both correlates, alone, can cue the voicing contrast, listeners weight VOT more heavily when both are available. Such differential weighting may arise from differences in the perceptual distance between voicing categories along the VOT versus onset F0 dimensions, or it may arise from a bias to pay more attention to VOT than to onset F0. The present experiment examines listeners' use of these two cues when classifying stimuli in which perceptual distance was artificially equated along the two dimensions. Listeners were also trained to categorize stimuli based on one cue at the expense of another. Equating perceptual distance eliminated the expected bias toward VOT before training, but successfully learning to base decisions more on VOT and less on onset F0 was easier than vice versa. Perceptual distance along both dimensions increased for both groups after training, but only VOT-trained listeners showed a decrease in Garner interference. Results lend qualified support to an attentional model of phonetic learning in which learning involves strategic redeployment of selective attention across integral acoustic cues.

Developmental changes in the weighting of prosodic cues

Previous research has shown that the weighting of, or attention to, acoustic cues at the level of the segment changes over the course of development (Nittrouer & Miller, 1997; Nittrouer, Manning & Meyer, 1993). In this paper we examined changes over the course of development in weighting of acoustic cues at the suprasegmental level. Specifically, we tested English-learning 4-month-olds' performance on a clause segmentation task when each of three acoustic cues to clausal units was neutralized and contrasted it with performance on a Baseline condition where no cues were manipulated. Comparison with the reported performance of 6-month-olds on the same task (Seidl, 2007) reveals that 4-month-olds weight prosodic cues to clausal boundaries differently than 6-month-olds, relying more heavily on all three correlates of clausal boundaries (pause, pitch and vowel duration) than 6-month-olds do, who rely primarily on pitch. We interpret this as evidence that 4-month-olds use a holistic processing strategy, while 6-month-olds may already be able to attend separately to isolated cues in the input stream and may, furthermore, be able to exploit a language-specific cue weighting. Thus, in a way similar to that in other cognitive domains, infants begin as holistic auditory scene processors and are only later able to process individual auditory cues.

Sensitivity to rhythmic parameters in dyslexic children: a comparison of Hungarian and English

It has been proposed that sensitivity to the parameters underlying speech rhythm may be important in setting up well-specified phonological representations in the mental lexicon. However, different acoustic parameters may contribute differentially to rhythm and stress in different languages. Here we contrast sensitivity to one such cue, amplitude envelope onset (rise time), in dyslexic and normally-developing children in two languages, Hungarian and English, ages from 7 to 11. Dyslexic and control children received phonological tasks, reading and spelling tasks and auditory processing tasks. While sensitivity to rise time was related to phonological representation in both languages, clear differences were found between languages. It is suggested that these differences may reflect differential language-specific weighting of different acoustic cues to rhythm and stress.

Selective attention and perceptual learning of speech

Phonetic experience can change the perceptual distance between speech sounds, increasing both within-category similarity and between-category distinctiveness. Such warping of perceptual space is frequently characterized in terms of changes in selective attention: Listeners are assumed to attend more strongly to category-differentiating features while ignoring less relevant ones. However, the link between the distribution of selective attention and categorization-related differences in perceptual distance has not been empirically demonstrated. To explore this relationship, listeners were given 6 h of training to categorize sounds according to one of two acoustic features while ignoring the other. The features were voice onset time and onset f0, which are normally correlated and can both serve as a cue to consonant voicing. Before and after training, listener’s performance on a Garner selective attention task was compared with assessment of the perceptual distance between tokens. Results suggest that training can induce both warping of perceptual space and changes in the distribution of selective attention, but the two phenomena are not necessarily related. Results are consistent with a two-stage model of perceptual learning, involving both preattentive adjustment of acoustic cue weighting and higher-level changes in the distribution of selective attention between acoustic cues. [Work supported by NIH-NIDCD 1R03DC006811.]

Erratum: “Adult-child differences in acoustic cue weighting are influenced by segmental context: Children are not always perceptually biased toward transitions” [J. Acoust. Soc. Am. 115, 3184–3194 (2004)

Erratum: “Adult-child differences in acoustic cue weighting are influenced by segmental context: Children are not always perceptually biased toward transitions” [J. Acoust. Soc. Am. 115, 3184–3194 (2004)

Erratum: “The influence of spectral distinctiveness on acoustic cue weighting in children's and adults' speech perception” [J. Acoust. Soc. Am. 118, 1730–1741 (2005)

Erratum: “The influence of spectral distinctiveness on acoustic cue weighting in children's and adults' speech perception” [J. Acoust. Soc. Am. 118, 1730–1741 (2005)

The influence of spectral distinctiveness on acoustic cue weighting in children’s and adults’ speech perception

Children and adults appear to weight some acoustic cues differently in perceiving certain speech contrasts. One possible explanation for this difference is that children and adults make use of different strategies in the way that they process speech. An alternative explanation is that adult-child cue weighting differences are due to more general sensory (auditory) processing differences between the two groups. It has been proposed that children may be less able to deal with incomplete or insufficient acoustic information than are adults, and thus may require cues that are longer, louder, or more spectrally distinct to identify or discriminate between auditory stimuli. The current study tested this hypothesis by examining adults' and 3- to 7-year-old children's cue weighting for contrasts in which vowel-onset formant transitions varied from spectrally distinct (/no/-/mo/, /do/-/bo/, and /ta/-/da/) to spectrally similar (/ni/-/mi/, /de/-/be/, and /ti/-/di/). Spectrally distinct cues were more likely to yield different consonantal responses than were spectrally similar cues, for all listeners. Furthermore, as predicted by a sensory hypothesis, children were less likely to give different consonantal responses to stimuli distinguished by spectrally similar transitional cues than were adults. However, this pattern of behavior did not hold for all contrasts. Implications for theories of adult-child cue weighting differences are discussed.

Adult-child differences in acoustic cue weighting are influenced by segmental context: children are not always perceptually biased toward transitions.

It has been proposed that young children may have a perceptual preference for transitional cues [Nittrouer, S. (2002). J. Acoust. Soc. Am. 112, 711-719]. According to this proposal, this preference can manifest itself either as heavier weighting of transitional cues by children than by adults, or as heavier weighting of transitional cues than of other, more static, cues by children. This study tested this hypothesis by examining adults' and children's cue weighting for the contrasts /saI/-/integral of aI/, /de/-/be/, /ta/-/da/, and /ti/-/di/. Children were found to weight transitions more heavily than did adults for the fricative contrast /saI/-/integral aI/, and were found to weight transitional cues more heavily than nontransitional cues for the voice-onset-time contrast /ta/-/da/. However, these two patterns of cue weighting were not found to hold for the contrasts /de/-/be/ and /ti/-/di/. Consistent with several studies in the literature, results suggest that children do not always show a bias towards vowel-formant transitions, but that cue weighting can differ according to segmental context, and possibly the physical distinctiveness of available acoustic cues.

Flexibility of acoustic cue weighting in children’s speech perception

Nittrouer and colleagues [Nittrouer, J. Phonetics 20, 1–32 (1992); Nittrouer and Miller, J Acoust. Soc. Am. 101, 2253–2265 (1997); Nittrouer et al., Percept. Psychophys. 62 (2000)] have found that in identifying certain syllable contrasts, young children make more use of syllable–internal formant transitions (relative to other available acoustic cues) than do older children and adults. The evidence for this change in the degree to which listeners weight, or use, certain cues comes predominantly from studies of fricative contrasts (e.g., /sV/–/∫V/, /sV/–/stV/, /Vs/–/V∫/). The current study tests the flexibility of children’s weighting of acoustic cues by examining cue weighting across a wider range of phonetic contexts. In particular, this study attempts to determine whether children’s focus of perceptual attention can be led away from transitions in contexts where such cues are relatively less salient. Additionally, the study tests children’s ability to identify phonemes in an extreme situation, in the complete absence of transitional information. [Work supported by Wellcome Trust.]

The perceptual weighting of acoustic cues changes with linguistic experience

Previous studies found that children’s judgments of syllable-initial /s/ and /∫/ are more related to the vocalic F2 transition and less related to the fricative-noise spectrum than are adults’ judgments [e.g., Nittrouer, J. Phon. 20, 351–382 (1992)]. Such results have led to a model of speech development proposing that children’s weighting of acoustic cues changes as they gain linguistic experience. The present study tested two requisites of that model, namely that the perceptual weighting of acoustic cues must be flexible and cannot simply reflect a listener’s auditory sensitivities. Adults and 3-year olds participated in two tasks: Identification tasks, using synthetic fricative noises and either natural or synthetic vocalic portions; and discrimination tasks, measuring sensitivity to fricative-noise spectrum and F2 transition. Identification tasks showed the same age-related differences found in earlier studies when natural vocalic portions were used, but these age effects were reduced when synthetic vocalic portions were used. Discrimination tasks showed slightly larger difference thresholds for both the fricative noise and the F2 transition for children than for adults, but this age effect could not explain the age effect on the weighting of those cues for identification. It was concluded that the weighting of acoustic cues is flexible both for adults and for children, and that age-related differences in the weighting of the cues to /s/ and /∫/ are not explained by age-related differences in auditory sensitivities. [Work supported by NIH.]

Perception and Production of a Voicing Contrast by French-English Bilinguals

The use of spectral information at vowel onset, which constitutes a stronger cue to the voicing contrast in English than in French, was investigated in French-English bilinguals in order to determine whether the primary language in terms of early experience determines acoustic cue weighting. The /pεn/-/bεn/ minimal pair, meaningful in both languages, was used as a base for identification tests, which were presented with either an English or a French precursor word before each token. Two stimulus continua, formed of digitally-edited natural speech tokens, had an identical VOT range but varied in their [εn] stem. In their production of the contrast, bilinguals showed clear evidence of code-switching but did not always produce monolingual-like VOTs in their weaker language. In perception, the code-switching effect was significant but small. The bilingual group with English as primary early language showed a greater effect of vowel onset characteristics, in conflictingcue conditions, than the bilingual group with French as their primary early language, and, on average, cue-weighting was not affected by the language of the precursor. An effect of language dominance on cue-weighting was therefore found.