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Information for Mandarin tones in the amplitude contour and in brief segments.

While the tones of Mandarin are conveyed mainly by the F0 contour, they also differ consistently in duration and in amplitude contour. The contribution of these factors was examined by using signal-correlated noise stimuli, in which natural speech is manipulated so that it has no F0 or formant structure but retains its original amplitude contour and duration. Tones 2, 3 and 4 were perceptible from just the amplitude contour, even when duration was not also a cue. In two further experiments, the location of the critical information for the tones during the course of the syllable was examined by extracting small segments from each part of the original syllable. Tones 2 and 3 were often confused with each other, and segments which did not have much F0 change were most often heard as Tone 1. There were, though, also cases in which a low, unchanging pitch was heard as Tone 3, indicating a partial effect of register even in Mandarin. F0 was positively correlated with amplitude, even when both were computed on a pitch period basis. Taken together, the results show that Mandarin tones are realized in more than just the F0 pattern, that amplitude contours can be used by listeners as cues for tone identification, and that not every portion of the F0 pattern unambiguously indicates the original tone.

Adult↗

Production and perception of coarticulated tones.

In the present study, the distinctive tones of Mandarin were found to coarticulate with adjacent tones in running speech. However, the amount of deviation of a tone from its canonical form due to coarticulation varied depending on the nature of the tonal context. In a context where adjacent tonal values agree (a "compatible" context), the deviation was relatively small. In a context where adjacent tonal values disagree (a "conflicting" context), the deviation was much greater, sometimes even to the extent of changing the direction of a dynamic tone. To examine the perception of coarticulated tones, naturally produced words and phrases were used as stimuli for tone identification. However, their semantic information was removed through waveform editing while all the tonal information contained in the signal remained intact. Identification of tones in the compatible context was highly accurate with or without the original tonal context. Tonal identification for the conflicting context remained accurate only when the tones were presented with the original tonal context. Without the original context, i.e., in isolation, correct tone identification dropped below chance. When the original tonal context was altered, listeners compensated for the altered context as if it had been there originally. It thus seems that, in tone perception, listeners compensate for variations due to coarticulation. Nevertheless, even with the presence of the original context, perceptual identification was better for the compatible context than for the conflicting context, indicating that variation due to coarticulation is not always completely compensated for by listeners.

Adult↗

Why stress position bias?

There is ample evidence in the literature that English and Dutch listeners tend to perceive stress on the word-initial syllable. This bias is most easily seen in the perception of (nonsense) words containing repetitions of identical syllables. In four experiments the possible causes of this bias are investigated. The results show that the bias disappears when (i) words are preceded by a spoken context, when (ii) the voice source is replaced by noise (whisper), or when (iii) the fundamental frequency level of the utterance as a whole is lowered. The data are best explained by assuming that the listener interprets the onset of voicing of an isolated word as a (silent) pitch rise from the bottom of the speaker's pitch range.

Humans↗

Musically tone-deaf individuals have difficulty discriminating intonation contours extracted from speech.

Musically tone-deaf individuals have psychophysical deficits in detecting pitch changes, yet their discrimination of intonation contours in speech appears to be normal. One hypothesis for this dissociation is that intonation contours use coarse pitch contrasts which exceed the pitch-change detection thresholds of tone-deaf individuals (). We test this idea by presenting intonation contours for discrimination, both in the context of the original sentences in which they occur and in a "pure" form dissociated from any phonetic context. The pure form consists of gliding-pitch analogs of the original intonation contours which exactly follow their pattern of pitch and timing. If the spared intonation perception of tone-deaf individuals is due to the coarse pitch contrasts of intonation, then such individuals should discriminate the original sentences and the gliding-pitch analogs equally well. In contrast, we find that discrimination of the gliding-pitch analogs is severely degraded. Thus it appears that the dissociation between spoken and musical pitch perception in tone-deaf individuals is due to a deficit at a higher level than simple pitch-change detection.

Adult↗

Semantic processing of unattended meaning is modulated by additional task load: evidence from electrophysiology.

Recently, we observed that the perception of word meaning, as measured with the N400 component of the event-related brain potential, is delayed but unimpaired by various additional tasks when the language task requires the processing of semantic properties of the word stimuli. In the present study, we assessed whether similar effects would be observed when the language task relates to acoustic rather than to semantic properties of the word stimuli. The N400 was elicited by synonymous and non-synonymous spoken noun pairs that were to be classified according to tone pitch. In a single task experiment, there was a small but clear synonymity effect in ERPs (N400), indicating the availability of word meaning to the semantic system. Additional processing load, imposed by an overlapping task, abolished N400 for all SOAs when stimulus-response assignments were incompatible. For compatible assignments, N400 amplitude was present but much attenuated at the longest SOA. We conclude that the availability of task-irrelevant meaning is modulated by additional task load and decay in short-term memory.

Adult↗

Lateralization for pure tone perception as a function of age and sex.

Pure tone thresholds were obtained for right and left ears from 195 males and 82 females aged 24-84. Right ear advantages were present and increased with advanced age for the males; no ear differences were found for females. These data may explain contradictions in the dichotic listening literature testing lateralization for language across the lifespan.

Adult↗

Burst and transition cues to voicing perception for spoken initial stops by impaired- and normal-hearing listeners.

The use of cues to voicing perception of initial stop consonants in multiple spoken syllables was studied for moderately/severely hearing-impaired (n = 43) and normal-hearing listeners (n = 12). The test stimuli were ten utterances each of the syllables/baed, gaed, daed, paed, kaed, taed/. The utterances were analyzed acoustically to confirm the presence of certain cues to initial-stop voicing, namely, differences in voice onset time (VOT), aspiration, and vowel-onset values of the first formant and of fundamental frequency (fo). Test conditions were prepared in which different portions of the syllable onsets were either deleted or interchanged for voicing-cognate syllables. Also the fo contour was flattened for syllable pairs via analysis/synthesis using linear predictor code (LPC) processing. The results confirmed that VOT was a strong voicing cue for both the hearing-impaired and normal-hearing listeners. When the aspirations of the voiceless stops were inserted between the release and the vowel of the voiced-stop syllables, the normal-hearing listeners perceived voiceless stops predominantly. The transition portions of the vowel onsets in burstless /baed, gaed, daed/ contained strong cues for voicing perception of /b,g,d/. The hearing-impaired listeners seemed less sensitive than the normal-hearing listeners to the aspiration-presence and the vowel-onset cues. The fo difference at vowel onset appeared to have no cue value for either group of listeners.

Adult↗

Perception of the envelope-beat frequency of inharmonic complex temporal envelopes.

Listeners can hear slow sinusoidal variations in the depth of sinusoidally amplitude-modulated (SAM) stimuli. Here, the SAM stimulus of frequency f(m) acts as the carrier, and the slow variation in depth of frequency f'm (referred to as "second-order" amplitude modulation) corresponds to a beat in the temporal envelope. Recent studies have suggested that second-order amplitude modulation perception is based on a modulation-distortion component or the "venelope" (the Hilbert envelope of the ac-coupled Hilbert envelope), both occurring at the envelope-beat frequency f'm. This was tested by transposing to the modulation domain the matching paradigm used by Schouten et al. [J. Acoust. Soc. Am. 34, 1418-1424 (1962)]. Listeners estimated the envelope-beat frequency evoked by a 5-Hz, second-order SAM white noise with f(m) either an integer multiple of f'm or shifted in frequency to make the complex envelope inharmonic. The results indicate that the perception of the envelope-beat frequency was affected by these shifts when f(m) < or = 20 Hz. This suggests that, at least at low modulation frequencies, the perceived envelope beat is not determined by a modulation-distortion or venelope component, but rather relies on the time intervals between the main peaks of the first-order envelope.

Acoustic Stimulation↗

Perceptual dissimilarities among acoustic stimuli and ipsilateral electric stimuli.

Five users of cochlear implants who had residual acoustic hearing in the implanted ear postoperatively participated in a study comparing the percepts elicited by acoustic and electric stimuli. The stimuli comprised pulse trains delivered to single electrodes and pure tones presented ipsilaterally. In the experiments, 12 equally loud stimuli with differing frequencies, electrode positions, and pulse rates were generated. Subjects listened to all of the possible pairs of stimuli in each set, and provided a relative dissimilarity rating for the members of each stimulus pair. The data were analyzed using non-metric multi-dimensional scaling techniques. Stimulus spaces were plotted in two dimensions to represent the results for each subject with each stimulus set. The results suggested that one dimension was associated with a pitch-like percept, related to the acoustic tone frequency and the active electrode position. The second dimension separated the acoustic stimuli from the electric stimuli. Generally, the electric pulse rate seemed to have a relatively small perceptual effect in this experimental context. Overall, the results show that acoustic pure tones are perceived as very different from electric pulse trains delivered to single electrode positions with constant rate, even when both the acoustic and the electric stimuli are presented to the same ear.

Acoustic Stimulation↗

Perceptual differences between vowels located in a limited phonetic space.

The perception of subphonemic differences between vowels was investigated using multidimensional scaling techniques. Three experiments were conducted with natural-sounding synthetic stimuli generated by linear predictive coding (LPC) formant synthesizers. In the first experiment, vowel sets near the pairs (i-I), (epsilon-ae), or (u-U) were synthesized containing 11 vowels each. Listeners judged the dissimilarities between all pairs of vowels within a set several times. These perceptual differences were mapped into distances between the vowels in an n-dimensional space using two-way multidimensional scaling. Results for each vowel set showed that the physical stimulus space, which was specified by the two parameters F1 and F2, was always mapped into a two-dimensional perceptual space. The best metric for modeling the perceptual distances was the Euclidean distance between F1 and F2 in barks. The second experiment investigated the perception of the same vowels from the first experiment, but embedded in a consonantal context. Following the same procedures as experiment 1, listeners' perception of the (bv) dissimilarities was not different from their perception of the isolated vowel dissimilarities. The third experiment investigated dissimilarity judgments for the three vowels (ae-alpha-lambda) located symmetrically in the F1 X F2 vowel space. While the perceptual space was again two dimensional, the influence of phonetic identity on vowel difference judgments was observed. Implications for determining metrics for subphonemic vowel differences using multidimensional scaling are discussed.

Adult↗

On the (non)categorical perception of lexical tones.

Identification and discrimination of lexical tones in Cantonese were compared in the context of a traditional categorical perception paradigm. Three lexical tone continua were used: one ranging from low level to high level, one from high rising to high level, and one from low falling to high rising. Identification data showed steep slopes at category boundaries, suggesting that lexical tones are perceived categorically. In contrast, discrimination curves generally showed much weaker evidence for categorical perception. Subsequent investigation showed that the presence of a tonal context played a strong role in the identification of target tones and less of a role in discrimination. The results are consistent with the hypothesis that tonal category boundaries are determined by a combination of regions of natural auditory sensitivity and the influence of linguistic experience.

Adult↗

The effects of short-term training for spectrally mismatched noise-band speech.

The present study examined the effects of short-term perceptual training on normal-hearing listeners' ability to adapt to spectrally altered speech patterns. Using noise-band vocoder processing, acoustic information was spectrally distorted by shifting speech information from one frequency region to another. Six subjects were tested with spectrally shifted sentences after five days of practice with upwardly shifted training sentences. Training with upwardly shifted sentences significantly improved recognition of upwardly shifted speech; recognition of downwardly shifted speech was nearly unchanged. Three subjects were later trained with downwardly shifted speech. Results showed that the mean improvement was comparable to that observed with the upwardly shifted training. In this retrain and retest condition, performance was largely unchanged for upwardly shifted sentence recognition, suggesting that these listeners had retained some of the improved speech perception resulting from the previous training. The results suggest that listeners are able to partially adapt to a spectral shift in acoustic speech patterns over the short-term, given sufficient training. However, the improvement was localized to where the spectral shift was trained, as no change in performance was observed for spectrally altered speech outside of the trained regions.

Adult↗

The use of a temporary extracochlear electrode in preoperative testing of permanent implant candidates.

This paper describes hearing and speech perception in 9 post-lingually deaf adults fitted with a temporary single electrode, surgically positioned close to the round window niche. After baseline testing, unaided and aided binaurally with the high-power Phonic Ear PE 845, each subject was admitted to hospital for a period of 7 days. During each test session, stimuli were presented directly to the electrode lead by means of an isolation unit. Current thresholds, upper tolerable limits and gap detection were measured for various acoustical waveforms and stimulus frequencies. A laryngograph was used to test the discrimination of prelinguistic and suprasegmental speech features. The results indicated that the prosthesis could provide acoustic sensations of loudness, pitch and duration that changed with stimulus waveform, level of current and frequency, and a gap threshold less than 50 msec. Lipreading appeared to be a necessary adjunct for consonant discrimination.

Adult↗

Ultrasonic hearing in humans: applications for tinnitus treatment.

Masking of tinnitus is possible using high audio frequencies and low-frequency ultrasound. The mechanisms involved in reception and perception of both audio frequencies and ultrasound are identical, with the exception that ultrasound interacts with an intermediary site, the brain. We proposed brain ultrasonic demodulation as the means of place-mapping ultrasound on the first few millimeters of the basilar membrane. We present modeling and psychoacoustic data in support of this theory.

Acoustic Stimulation↗

Speech and melody recognition in binaurally combined acoustic and electric hearing.

Speech recognition in noise and music perception is especially challenging for current cochlear implant users. The present study utilizes the residual acoustic hearing in the nonimplanted ear in five cochlear implant users to elucidate the role of temporal fine structure at low frequencies in auditory perception and to test the hypothesis that combined acoustic and electric hearing produces better performance than either mode alone. The first experiment measured speech recognition in the presence of competing noise. It was found that, although the residual low-frequency (<1000 Hz) acoustic hearing produced essentially no recognition for speech recognition in noise, it significantly enhanced performance when combined with the electric hearing. The second experiment measured melody recognition in the same group of subjects and found that, contrary to the speech recognition result, the low-frequency acoustic hearing produced significantly better performance than the electric hearing. It is hypothesized that listeners with combined acoustic and electric hearing might use the correlation between the salient pitch in low-frequency acoustic hearing and the weak pitch in the envelope to enhance segregation between signal and noise. The present study suggests the importance and urgency of accurately encoding the fine-structure cue in cochlear implants.

Acoustic Stimulation↗

Modeling complex tone perception: grouping harmonics with combination-sensitive neurons.

Perception of complex communication sounds is a major function of the auditory system. To create a coherent precept of these sounds the auditory system may instantaneously group or bind multiple harmonics within complex sounds. This perception strategy simplifies further processing of complex sounds and facilitates their meaningful integration with other sensory inputs. Based on experimental data and a realistic model, we propose that associative learning of combinations of harmonic frequencies and nonlinear facilitation of responses to those combinations, also referred to as "combination-sensitivity," are important for spectral grouping. For our model, we simulated combination sensitivity using Hebbian and associative types of synaptic plasticity in auditory neurons. We also provided a parallel tonotopic input that converges and diverges within the network. Neurons in higher-order layers of the network exhibited an emergent property of multifrequency tuning that is consistent with experimental findings. Furthermore, this network had the capacity to "recognize" the pitch or fundamental frequency of a harmonic tone complex even when the fundamental frequency itself was missing.

Animals↗

The effects of musical training and cerebral asymmetries on perception of an auditory illusion.

Twenty-seven right- and fourteen left-handed subjects with varying amounts of musical training listened to dichotic octave patterns. Each pattern consisted of twenty 250-msec. tones which oscillated from 400 to 800 Hz. Patterns were combined in such a way that while one ear received a 400 Hz tone, an 800 Hz tone was simultaneously present in the opposite ear. Reported perception of these patterns was significantly related to the handedness of the subjects. In addition, responses of subjects with musical training differed significantly from those of untrained subjects. An hypothesis is suggested that musical training serves to establish a sharper psychophysical criterion for judging unfamiliar sounds. Further research should be directed toward understanding the relationship between the octave illusion and cerebral dominance.

Adolescent↗

Discrimination of temporal information at the cerebellum: functional magnetic resonance imaging of nonverbal auditory memory.

Until recently, the cerebellum was held to play its chief role in motor control. By contrast, Keele and Ivry (1990) proposed that it may subserve time estimation within the perceptual domain as well. In accordance with this suggestion, speech perception requiring minute differentiation of time intervals was found compromised by cerebellar pathology a subsequent functional magnetic resonance imaging (fMRI) study found hemodynamic activation of the right neocerebellum under these conditions. In the current fMRI investigation a non-speech task involving duration storage and comparison yielded significant hemodynamic responses within the lateral Crus I area of the right cerebellar hemisphere. Concomitantly, a left prefrontal cluster was observed. The present fMRI study employed single-shot double-echo echo-planar imaging (EPI) to reduce image distortion and acquisition time with whole-brain coverage (TE = 28 and 66 ms, TR = 5 s, 28 slices, TA = 2.8 s). Twelve healthy subjects performed two tasks: identifying pauses between tones as "short" or "long" (30-130 ms) and deciding which of two successive pauses was longer. The activation pattern in the discrimination task was analogous to that seen during speech perception and verbal working memory (WM) tasks. We suggest that the storage of precise temporal structures relies on a cerebellar-prefrontal loop. This network allows for temporal organization of verbal sequences and phoneme encoding based on durational operations in a linguistic context.

Adult↗