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The current work examines native Korean speakers’ perception and production of stop contrasts in their native language (L1, Korean) and second language (L2, English), focusing on three acoustic dimensions that are all used, albeit to different extents, in both languages: voice onset time (VOT), f0 at vowel onset, and closure duration. Participants used all three cues to distinguish the L1 Korean three-way stop distinction in both production and perception. Speakers’ productions of the L2 English contrasts were reliably distinguished using both VOT and f0 (even though f0 is only a very weak cue to the English contrast), and, to a lesser extent, closure duration. In contrast to the relative homogeneity of the L2 productions, group patterns on a forced-choice perception task were less clear-cut, due to considerable individual differences in perceptual categorization strategies, with listeners using either primarily VOT duration, primarily f0, or both dimensions equally to distinguish the L2 English contrast. Differences in perception, which were stable across experimental sessions, were not predicted by individual variation in production patterns. This work suggests that reliance on multiple cues in representation of a phonetic contrast can form the basis for distinct individual cue-weighting strategies in phonetic categorization.

Purpose Computational modeling was used to examine the consequences of 5 different laryngeal asymmetries on acoustic and perceptual measures of vocal function. Method A kinematic vocal fold model was used to impose 5 laryngeal asymmetries: adduction, edge bulging, nodal point ratio, amplitude of vibration, and starting phase. Thirty /a/ and /ɪ/ vowels were generated for each asymmetry and analyzed acoustically using cepstral peak prominence (CPP), harmonics-to-noise ratio (HNR), and 3 measures of spectral slope (H1*-H2*, B0-B1, and B0-B2). Twenty listeners rated voice quality for a subset of the productions. Results Increasingly asymmetric adduction, bulging, and nodal point ratio explained significant variance in perceptual rating ( R 2 = .05, p < .001). The same factors resulted in generally decreasing CPP, HNR, and B0-B2 and in increasing B0-B1. Of the acoustic measures, only CPP explained significant variance in perceived quality ( R 2 = .14, p < .001). Increasingly asymmetric amplitude of vibration or starting phase minimally altered vocal function or voice quality. Conclusion Asymmetries of adduction, bulging, and nodal point ratio drove acoustic measures and perception in the current study, whereas asymmetric amplitude of vibration and starting phase demonstrated minimal influence on the acoustic signal or voice quality. Supplemental Material https://doi.org/10.23641/asha.6170459

Previous work has shown that human listeners are sensitive to level differences in high-frequency energy (HFE) in isolated vowel sounds produced by male singers. Results indicated that sensitivity to HFE level changes increased with overall HFE level, suggesting that listeners would be more “tuned” to HFE in vocal production exhibiting higher levels of HFE. It follows that sensitivity to HFE level changes should be higher (1) for female vocal production than for male vocal production and (2) for singing than for speech. To test this hypothesis, difference limens for HFE level changes in male and female speech and singing were obtained. Listeners showed significantly greater ability to detect level changes in singing vs speech but not in female vs male speech. Mean differences limen scores for speech and singing were about 5 dB in the 8-kHz octave (5.6–11.3 kHz) but 8–10 dB in the 16-kHz octave (11.3–22 kHz). These scores are lower (better) than those previously reported for isolated vowels and some musical instruments.

Purpose This study investigated an account of limited short-term memory capacity for children’s speech perception in noise using a dual-task paradigm. Method Sixty-four normal-hearing children (7–14 years of age) participated in this study. Dual tasks were repeating monosyllabic words presented in noise at 8 dB signal-to-noise ratio and rehearsing sets of 3 or 5 digits for subsequent serial recall. Half of the children were told to allocate their primary attention to word repetition and the other half to remembering digits. Dual-task performance was compared to single-task performance. Limitations in short-term memory demands required for the primary task were measured by dual-task decrements in nonprimary tasks. Results Results revealed that (a) regardless of task priority, no dual-task decrements were found for word recognition, but significant dual-task decrements were found for digit recall; (b) most children did not show the ability to allocate attention preferentially to primary tasks; and (c) younger children (7- to 10-year-olds) demonstrated improved word recognition in the dual-task conditions relative to their single-task performance. Conclusions Seven- to 8-year-old children showed the greatest improvement in word recognition at the expense of the greatest decrement in digit recall during dual tasks. Several possibilities for improved word recognition in the dual-task conditions are discussed.

Given the interest in comparing speech production development in children with normal hearing and hearing impairment, it is important to evaluate how variables within speech elicitation tasks can differentially affect the acoustics of speech production for these groups. In a first experiment, children (6–14 years old) with cochlear implants produced a set of monosyllabic words either in isolation or while simultaneously signing the word. Acoustical analyses indicated no change in word duration, voice onset time, intensity, or fundamental frequency between isolated and simultaneous signing conditions. In a second experiment, the same children verbally repeated words that were signed by a video model. The model either signed with inflection or without. Words repeated after inflected models were higher in fundamental frequency and intensity and were more intelligible. In addition, children with poorer speech perception skills sometimes produced the monosyllables as 2 syllables, but this only occurred for words that had multiple sign movements. The results have implications for the comparison of speech development between children with normal hearing and those with hearing impairment.

The ability to integrate and weight information across dimensions is central to perception and is particularly important for speech categorization. The present experiments investigate cue weighting by training participants to categorize sounds drawn from a two-dimensional acoustic space defined by the center frequency (CF) and modulation frequency (MF) of frequency-modulated sine waves. These dimensions were psychophysically matched to be equally discriminable and, in the first experiment, were equally informative for accurate categorization. Nevertheless, listeners' category responses reflected a bias for use of CF. This bias remained even when the informativeness of CF was decreased by shifting distributions to create more overlap in CF. A reversal of weighting (MF over CF) was obtained when distribution variance was increased for CF. These results demonstrate that even when equally informative and discriminable, acoustic cues are not necessarily equally weighted in categorization; listeners exhibit biases when integrating multiple acoustic dimensions. Moreover, changes in weighting strategies can be affected by changes in input distribution parameters. This methodology provides potential insights into acquisition of speech sound categories, particularly second language categories. One implication is that ineffective cue weighting strategies for phonetic categories may be alleviated by manipulating variance of uninformative dimensions in training stimuli.

Recently, Holt and Lotto [Hear. Res. 167, 156–169 (2002)] reported that preceding speech sounds can influence phonetic identification of a target syllable even when the context sounds are presented to the opposite ear or when there is a long intervening silence. These results led them to conclude that phonetic context effects are mostly due to nonperipheral auditory interactions. In the present paper, similar presentation manipulations were made with nonspeech context sounds. The results agree qualitatively with the results for speech contexts. Taken together, these findings suggest that the same nonperipheral mechanisms may be responsible for effects of both speech and nonspeech context on phonetic identification.

One of the central findings of speech perception is that identical acoustic signals can be perceived as different speech sounds depending on adjacent speech context. Although these phonetic context effects are ubiquitous in speech perception, their neural mechanisms remain largely unknown. The present work presents a review of recent data suggesting that spectral content of speech mediates phonetic context effects and argues that these effects are likely to be governed by general auditory processes. A descriptive framework known as spectral contrast is presented as a means of interpreting these findings. Finally, and most centrally, four behavioral experiments that begin to delineate the level of the auditory system at which interactions among stimulus components occur are described. Two of these experiments investigate the influence of diotic versus dichotic presentation upon two phonetic context effects. Results indicate that context effects remain even when context is presented to the ear contralateral to that of the target syllable. The other two experiments examine the time course of phonetic context effects by manipulating the silent interval between context and target syllables. These studies reveal that phonetic context effects persist for hundreds of milliseconds. Results are interpreted in terms of auditory mechanism with particular attention to the putative link between auditory enhancement and phonetic context effects.

Kluender et al. [J. Acoust. Soc. Am. 97, 2552-2567 (1995)] reported that overall stimulus amplitude affects perception of the voicing contrast in syllable-initial stops as a function of frequency separation between the first formant (F1) and higher formants (F2, F3). These results were offered as support for a hypothesis that [- voice] could be signaled by a shift in the temporal pattern of neural firing from synchronizing to energy at frequencies of F2 and F3 to synchronizing to energy near F1. Several predictions from this "synchrony capture hypothesis" were tested in the current study. In all cases the hypothesis was not supported. Effect of stimulus amplitude (increased voiceless responses with higher amplitude) was maintained when there was no cutback in F1 or when F2 and F1 energy bands were presented dichotically. In further tests of the hypothesis, voice-voiceless series were created that maintained periodic energy throughout the syllable (with F1 cutback signaling voicing). Energy just below the frequency of F2 and energy above F1 were presented dichotically. Thus, at the periphery there was no competition between frequencies near F2 and lower frequencies. In contrast to predictions of the "synchrony capture hypothesis," overall amplitude still had an effect on voice-voiceless identifications.

Bilinguals perceptually accommodate speech variation across languages, but to what extent this flexibility depends on bilingual experience is uncertain. One account suggests that bilingual experience promotes language-specific processing modes, implying that bilinguals can switch as appropriate between the different phonetic systems of the languages they speak. Another account suggests that bilinguals rapidly recalibrate to the unique acoustic properties of each language following language-general processes common to monolinguals. Challenging this latter account, the present results show that Spanish-English bilinguals with exposure to both languages from early childhood, but not English monolinguals, shift perception as appropriate across acoustically controlled English and Spanish contexts. Early bilingual experience appears to promote language-specific phonetic systems.

In response to stop consonants with longer F1-cutback duration, the dominant synchronization of mid- and high-CF chinchilla auditory-nerve fibers changes from frequencies near F2 to frequencies near F1 at onset of voicing [D. G. Sinex and L. P. McDonald, J. Acoust. Soc. Am. 85, 1995-2004 (1989)]. If this change in neural synchronization is perceptually relevant for human listeners, then it may be predicted that changes in stimulus intensity and changes in the frequency difference between lower (F1) and higher (F2/F3) stimulus components should both affect perception of voicing. In a series of experiments, multiple continua of synthesized CVs varying in F1 cutback of the consonantal portion were played to listeners at levels ranging from 40 to 80 dB SPL. Across experiments, the frequency difference between F1 and F2 was manipulated by changing the onset frequency of F1 or F2. Subjects labeled more initial stops as voiceless as a function of increasing stimulus level and of decreasing frequency difference between F1 and F2. There was also an interaction between stimulus intensity and the frequency difference between F1 and F2 such that the effect of intensity was greater for smaller differences. These effects were reliable across a number of synthetic F1-cutback series, and the effect of intensity extended to a digitally edited series of hybrid CVs in which F1-cutback was varied by cross splicing naturally produced /da/ and /ta/. The effect of overall stimulus intensity was not affected by amplitude of prevocalic aspiration energy or by the presence or absence of release bursts. The results provide evidence for the perceptual significance of synchrony encoding of voicing for stop consonants.

The human voice spectrum above 5 kHz receives little attention. However, there are reasons to believe that this high-frequency energy (HFE) may play a role in perceived quality of voice in singing and speech. To fulfill this role, differences in HFE must first be detectable. To determine human ability to detect differences in HFE, the levels of the 8- and 16-kHz center-frequency octave bands were individually attenuated in sustained vowel sounds produced by singers and presented to listeners. Relatively small changes in HFE were in fact detectable, suggesting that this frequency range potentially contributes to the perception of especially the singing voice. Detection ability was greater in the 8-kHz octave than in the 16-kHz octave and varied with band energy level.

Speech is commonly claimed to relate to mirror neurons because of the alluring surface analogy of mirror neurons to the Motor Theory of speech perception, which posits that perception and production draw upon common motor-articulatory representations. We argue that the analogy fails and highlight examples of systems-level developmental approaches that have been more fruitful in revealing perception–production associations.

In a previous paper, Lotto et al. [J. Acoust. Soc. Am. 103, 3648–3655 (1998)] claimed that experiments investigating a perceptual magnet effect (PME) failed to demonstrate a novel effect of goodness judgments on speech sound discrimination due to a confound in the procedure. New analyses of these data and a review of the recent literature fail once again to support the existence of PME.

Williams [(1986). "Role of dynamic information in the perception of coarticulated vowels," Ph.D. thesis, University of Connecticut, Standford, CT] demonstrated that nonspeech contexts had no influence on pitch judgments of nonspeech targets, whereas context effects were obtained when instructed to perceive the sounds as speech. On the other hand, Holt et al. [(2000). "Neighboring spectral content influences vowel identification," J. Acoust. Soc. Am. 108, 710-722] showed that nonspeech contexts were sufficient to elicit context effects in speech targets. The current study was to test a hypothesis that could explain the varying effectiveness of nonspeech contexts: Context effects are obtained only when there are well-established perceptual categories for the target stimuli. Experiment 1 examined context effects in speech and nonspeech signals using four series of stimuli: steady-state vowels that perceptually spanned from /inverted ohm/-/I/ in isolation and in the context of /w/ (with no steady-state portion) and two nonspeech sine-wave series that mimicked the acoustics of the speech series. In agreement with previous work context effects were obtained for speech contexts and targets but not for nonspeech analogs. Experiment 2 tested predictions of the hypothesis by testing for nonspeech context effects after the listeners had been trained to categorize the sounds. Following training, context-dependent categorization was obtained for nonspeech stimuli in the training group. These results are presented within a general perceptual-cognitive framework for speech perception research.

Purported units of speech, e.g. phonemes or features, are essentially categories. The assignment of phonemic (or phonetic) identity is a process of categorization: potentially discriminable speech sounds are treated in an equivalent manner. Unfortunately the extensive literature on human categorization has typically focused on simple visual categories that are defined by the presence or absence of discrete features. Speech categories are much more complex. They are often defined by continuous values across a variety of imperfectly valid features. In this paper, several kinds of categories are distinguished and studies using human subjects, animal subjects and computational models are presented that endeavor to describe the structure and development of the sort of complex categories underlying speech perception.

Across a variety of languages, phonation type and vocal-tract shape systematically covary in vowel production. Breathy phonation tends to accompany vowels produced with a raised tongue body and/or advanced tongue root. A potential explanation for this regularity, based on a hypothesized interaction between the acoustic effects of vocal-tract shape and phonation type, is evaluated. It is suggested that increased spectral tilt and first-harmonic amplitude resulting from breathy phonation interact with the lower-frequency first formant resulting from a raised tongue body to produce a perceptually ‘higher’ vowel. To test this hypothesis, breathy and modal versions of vowel series modelled after male and female productions of English vowel pairs /i/ and /i/, /u/ and /ω/, and /λ/ and /a/ were synthesized. Results indicate that for most cases, breathy voice quality led to more tokens being identified as the higher vowel (i.e. /i/, /u/, /ÊŒ/). In addition, the effect of voice quality is greater for vowels modelled after female productions. These results are consistent with a hypothesized perceptual explanation for the covariation of phonation type and tongue-root advancement in West African languages. The findings may also be relevant to gender differences in phonation type.

When F1‐onset frequency is lower, longer F1 cutback (VOT) is required for human listeners to perceive synthesized stop consonants as voiceless. K. R. Kluender [J. Acoust. Soc. Am. 90, 83–96 (1991)] found comparable effects of F1‐onset frequency on the ‘‘labeling’’ of stop consonants by Japanese quail (coturnix coturnix japonica) trained to distinguish stop consonants varying in F1 cutback. In that study, CVs were synthesized with naturallike rising F1 transitions, and endpoint training stimuli differed in the onset frequency of F1 because a longer cutback resulted in a higher F1 onset. In order to assess whether earlier results were due to auditory predispositions or due to animals having learned the natural covariance between F1 cutback and F1‐onset frequency, the present experiment was conducted with synthetic continua having either a relatively low (375 Hz) or high (750 Hz) constant‐frequency F1. Six birds were trained to respond differentially to endpoint stimuli from three series of synthesized /CV/s varying in duration of F1 cutback. Second and third formant transitions were appropriate for labial, alveolar, or velar stops. Despite the fact that there was no opportunity for animal subjects to use experienced covariation of F1‐onset frequency and F1 cutback, quail typically exhibited shorter labeling boundaries (more voiceless stops) for intermediate stimuli of the continua when F1 frequency was higher. Responses by human subjects listening to the same stimuli were also collected. Results lend support to the earlier conclusion that part or all of the effect of F1 onset frequency on perception of voicing may be adequately explained by general auditory processes. Implications concerning VOT variation for stop consonants at different places of articulation or preceding different vowels are discussed.

The present study was designed to investigate the effects of long‐term linguistic experience on the perception of non‐speech sounds in English and Spanish speakers. Research using tone‐onset‐time (TOT) stimuli, a type of non‐speech analogue of voice‐onset‐time (VOT) stimuli, has suggested that there is an underlying auditory basis for the perception of stop consonants based on a threshold for detecting onset asynchronies in the vicinity of +20 ms. For English listeners, stop consonant labeling boundaries are congruent with the positive auditory discontinuity, while Spanish speakers place their VOT labeling boundaries and discrimination peaks in the vicinity of 0 ms VOT. The present study addresses the question of whether long‐term linguistic experience with different VOT categories affects the perception of non‐speech stimuli that are analogous in their acoustic timing characteristics. A series of synthetic VOT stimuli and TOT stimuli were created for this study. Using language appropriate labeling and ABX discrimination tasks, labeling boundaries (VOT) and discrimination peaks (VOT and TOT) are assessed for 24 monolingual English speakers and 24 monolingual Spanish speakers. The interplay between language experience and auditory biases are discussed. [Work supported by NIDCD.]

Perception of the voicing contrast in CV syllables can be affected by the duration of the following vowel such that longer vowels lead to more ‘‘voiced’’ responses. On the basis of several experiments, Green, Stevens, and Kuhl [Percept. Psychophys. 55, 249–260 (1994)] concluded that continuity of pitch, but not continuity of formant structure, determined the effective length of the following vowel. In attempts to replicate these findings, it was found that both effects were highly dependent upon particular choices of pitch and formant values. First, discontinuity in pitch does not preclude the vowel‐length effect when fundamental frequency changes from 200 to 100 Hz and 200‐Hz partials extend continuously through test syllables. Second, spectral discontinuity does preclude the vowel‐length effect when formant changes result in a spectral peak moving to another harmonic. Even when perceived identity of the vowel remained constant, formant changes that resulted in a change in peak harmonic precluded the vow...

Perception of syllable‐initial /d/ and /g/ can be affected by the composition of preceding acoustic information such that, for a series of synthesized consonant‐vowel syllables (CVs) varying in onset characteristics of the third formant (F3) and varying perceptually from /da/ to /ga/, subjects are more likely to perceive /da/ when preceded by the syllable /al/, and to perceive /ga/ when preceded by /ar/ [V. A. Mann, Percept. Psychophys. 28, 407–412 (1980)]. In the present studies, this initial finding was replicated, and a second experiment was conducted to evaluate the extent to which the effect could be attributed to general properties of auditory perception. Members of a 10‐step series of /da‐ga/ syllables varying in F3 onset frequency were preceded by the syllables /ar/ and /al/ and by frequency modulated (FM) glide analogues of F3 from those syllables. Analogues were 150‐ms sine wave glides that followed the trajectory of F3 in /al/ or in /ar/, and were amplitude matched to the rms energy within a cr...

In Korean there are three classes of stops: Voiceless unaspirated [t], voiceless slightly aspirated [tb], and voiceless heavily aspirated [thh]. For these classes of stops produced by male and female Seoul and Pusan speakers, voice‐onset time (VOT), amplitude of aspiration, and f0 of the first five glottal pulses were measured. VOT was longer for slightly aspirated than for unaspirated stops, and longer still for heavily aspirated stops. Unaspirated and heavily aspirated stops were both produced with significantly higher f0 (more than 30%) than slightly aspirated stops. Gender and dialect (Seoul versus Pusan) differences in these variables were also noted. Then, six 12‐step series of syllables differing in VOT (5–82 ms), fundamental frequency (100, 125, 150 Hz), and amplitude of aspiration noise (−33, −21 dB re: vocalic energy) were synthesized. These stops, varying perceptually from [ta] to [tba] to [thha], were presented to 12 native‐Korean listeners. Results indicate that all three stimulus variables were perceptually significant for the Korean listeners. [Work supported by NIDCD Grant No. DC‐00719 and NSF Grant No. DBS‐9258482.]

Some acoustic instances of phonetic segments are phonemically more compelling than others, and studies involving human infants and monkeys suggest that experience plays a critical role in modifying the manner in which subjects respond to between and within phonetic category differences. In this study, eight European starlings (Sturnus vulgaris) were trained to discriminate vowel tokens drawn from stylized distributions either of the Engish vowel categories /i/ and /I/, or of the Swedish vowel categories /y/ and /I/. Following training, responses to novel stimuli drawn from these distributions indicated that starlings’ responses generalized with facility to novel category examples. Multiple linear regression analyses revealed that responses could be well predicted on the bases of F1 and F2 values and distributional characteristics of experienced vowel sounds. Responses manifested a graded structure about the central ‘‘prototypical’’ vowel of the training category. Starling response rates (/i‐I/birds) corre...

For a variety of East and West African languages, voice quality covaries with tongue root advancement. In these vowel systems, an advanced tongue root vowel is produced with breathy phonation, whereas, a modal voice quality is used with nonadvanced tongue root. A potential explanation for this regularity, based on the interaction between acoustic effects of vocal‐tract shape and of voice quality, was evaluated. Because it has been suggested that the advanced tongue root contrast is similar to the tense/lax contrast in English, male and female series varying perceptually from tense to lax were synthesized for several English vowels. Breathy versions of each series were created by increasing spectral tilt. Results from identification tasks indicated that, in general, breathy phonation led to more high vowels being identified as tense. In addition, the effect of breathiness was greater for vowels modeled after female productions. These results suggest that the covariation in African languages may be consistent with the general principle of auditory enhancement and adaptive dispersion. The findings may also be relevant to gender differences in voice quality. [Work supported by NIDCD Grant No. DC‐00719 and NSF Grant No. DBS‐9258482.]

Duration of attenuation in the region of the first formant (F1 cutback) and relative level of aspiration energy are known to be significant acoustic cues used to distinguish voiced from voiceless English stop consonants in initial position. This experiment was designed to test whether Korean listeners distinguish English stops on the same bases as native English listeners. In an identification task, 72 stimuli from six continua ranging perceptually from /da/ to /ta/ were presented to 12 Korean and 12 English subjects. Stimuli were synthesized using a parallel formant synthesizer and varied in duration of F1 cutback (5–82 ns in 7‐ms steps), relative amplitude of prevocalic aspiration energy, and fundamental frequency (100, 125, and 150 Hz) of vocalic energy. Longer F1‐cutback durations and greater aspiration intensity both significantly increased the proportion of voiceless /ta/ responses for both Korean and English subjects. Only Korean subjects labeled more stops as voiceless when fundamental frequency w...

In response to stop consonants differing in voice onset time (VOT), the dominant synchronization of mid‐CF chinchilla auditory nerve fibers changes from the frequencyof F2 to the frequency of F1 at onset of voicing [D. G. Sinex and J. P. McDonald, J. Acoust. Soc. Am. 85, 1995–2004 (1987)]. If this change in neutral synchronization is perceptually relevant for human listeners, changes in stimulus intensity and changes in the frequency difference between F1 and F2 should both affect perception of voicing. In a series of experiments, several continua of synthesized CV’s varying in VOT were played to listeners at levels ranging from 40 to 80 dB SPL. The frequency difference between F1 and F2 was manipulated through the use of different places of articulation and different following vowels. Subjects labeled more CV’s as voiceless as a function of increasing stimulus level and of deceasing F1–F2 frequency difference. There was also an interaction between stimulus intensity and F1–F2 frequency difference such that the effect of intensity was greater for smaller F1–F2 differences. These effects were reliable across a number of synthetic VOT series, and the effect of intensity extended to a computer edited series of hybrid CV’s in which VOT was varied by cross‐splicing a naturally produced /da/ and /ta/. The effect of overall stimulus intensity was not affected by amplitude of aspiration energy or by the presence or absence of release bursts. The results provide evidence for synchrony encoding of voicing for stop consonants. [Work supported by NIDCD/NIH Grant No. DC‐00719.]