Envelope-onset asynchrony as a cue to voicing in initial english consonants

An acoustic cue for voicing is proposed based on the underlying processes associated with the production of the voicing contrast. This cue is based on the time asynchrony between the onsets of two amplitude-envelope signals derived from different bands of speech (i.e., envelopes derived from a lowpass-filtered band at 350 Hz and from a highpass-filtered band at 3000 Hz). Acoustic measurements made on the envelope signals of a set of 16 initial consonants represented through multiple tokens of C1VC2 syllables indicate that the onset-timing difference between the low- and high-frequency envelopes (Envelope-Onset Asynchrony or EOA) provides a reliable and robust cue for distinguishing voiced from voiceless consonants. This cue, which is simply derived in real-time, has applications to the design of sensory aids for persons with profound hearing impairments (e.g., as a supplement to lipreading), as well as to automatic speech recognition.     

Preliminary observations on the use of duration as a cue to syllable-initial fricative consonant voicing in English

Acoustic analyses were undertaken to explore the durational characteristics of the fricatives [f,theta,s,v,delta z] as cues to initial consonant voicing in English. Based on reports on the perception of voiced-voiceless fricatives, it was expected that there would be clear-cut duration differences distinguishing voiced and voiceless fricatives. Preliminary results for three speakers indicate that, although differences emerged in the overall mean duration of voiced and voiceless fricatives, contrary to expectations, there was a great deal of overlap in the duration distribution of voiced and voiceless fricative tokens. Further research is needed to examine the role of duration as a cue to syllable-initial fricative consonant voicing in English.     

Differential cue weighting in perception and production of consonant voicing

This study examines English speakers' relative weighting of two voicing cues in production and perception. Participants repeated words differing in initial consonant voicing ([b] or [p]) and labeled synthesized tokens ranging between [ba] and [pa] orthogonally according to voice onset time (VOT) and onset f0. Discriminant function analysis and logistic regression were used to calculate individuals' relative weighting of each cue. Production results showed a significant negative correlation of VOT and onset f0, while perception results showed a trend toward a positive correlation. No significant correlations were found across perception and production, suggesting a complex relationship between the two domains.     

Acoustic and perceptual characteristics of voicing in fricatives and fricative clusters.

Several types of measurements were made to determine the acoustic characteristics that distinguish between voiced and voiceless fricatives in various phonetic environments. The selection of measurements was based on a theoretical analysis that indicated the acoustic and aerodynamic attributes at the boundaries between fricatives and vowels. As expected, glottal vibration extended over a longer time in the obstruent interval for voiced fricatives than for voiceless fricatives, and there were more extensive transitions of the first formant adjacent to voiced fricatives than for the voiceless cognates. When two fricatives with different voicing were adjacent, there were substantial modifications of these acoustic attributes, particularly for the syllable-final fricative. In some cases, these modifications leads to complete assimilation of the voicing feature. Several perceptual studies with synthetic vowel-consonant-vowel stimuli and with edited natural stimuli examined the role of consonant duration, extent and location of glottal vibration, and extent of formant transitions on the identification of the voicing characteristics of fricatives. The perceptual results were in general consistent with the acoustic observations and with expectations based on the theoretical model. The results suggest that listeners base their voicing judgments of intervocalic fricatives on an assessment of the time interval in the fricative during which there is no glottal vibration. This time interval must exceed about 60 ms if the fricative is to be judged as voiceless, except that a small correction to this threshold is applied depending on the extent to which the first-formant transitions are truncated at the consonant boundaries.     

Contralateral influences of wideband inhibition on the effect of onset asynchrony as a cue for auditory grouping

Onset asynchrony is an important cue for segregating sound mixtures. A harmonic of a vowel that begins before the other components contributes less to vowel quality. This asynchrony effect can be partly reversed by accompanying the leading portion of the harmonic with an octave-higher captor tone. The original interpretation was that the captor and leading portion formed a perceptual group, but it has recently been shown that the captor effect depends on neither a common onset time nor harmonic relations with the leading portion. Instead, it has been proposed that the captor effect depends on wideband inhibition in the central auditory system. Physiological evidence suggests that such inhibition occurs both within and across ears. Experiment 1 compared the efficacy of a pure-tone captor presented in the same or opposite ear to the vowel and leading harmonic. Contralateral presentation was at least as effective as ipsilateral presentation. Experiment 2 used multicomponent captors in a more comprehensive evaluation of harmonic influences on captor efficacy. Three captors with different fundamental frequencies were used, one of which formed a consecutive harmonic series with the leading harmonic. All captors were equally effective, irrespective of the harmonic relationship. These findings support and refine the inhibitory account.     

Tactual display of consonant voicing as a supplement to lipreading

This research is concerned with the development and evaluation of a tactual display of consonant voicing to supplement the information available through lipreading for persons with profound hearing impairment. The voicing cue selected is based on the envelope onset asynchrony derived from two different filtered bands (a low-pass band and a high-pass band) of speech. The amplitude envelope of each of the two bands was used to modulate a different carrier frequency which in turn was delivered to one of the two fingers of a tactual stimulating device. Perceptual evaluations of speech reception through this tactual display included the pairwise discrimination of consonants contrasting voicing and identification of a set of 16 consonants under conditions of the tactual cue alone (T), lipreading alone (L), and the combined condition (L + T). The tactual display was highly effective for discriminating voicing at the segmental level and provided a substantial benefit to lipreading on the consonant-identification task. No such benefits of the tactual cue were observed, however, for lipreading of words in sentences due perhaps to difficulties in integrating the tactual and visual cues and to insufficient training on the more difficult task of connected-speech reception.     

Testing performance of CIECAM02 in predicting perceptual contrast

A psychophysical experiment is performed on two large-size liquid crystal displays under three viewing conditions to assess perceptual contrast.Based on the visual data,the performance of CIECAM02 in predicting perceptual contrast under different viewing conditions is tested and compared with other models by F-test.Results show that the perceptual contrast models in the form of Weber contrast using CIECAM02 brightness Q agreed better with the contrast perception of human visual system compared to the models using luminance,CIELAB lightness L?,and CIECAM02 lightness J.     

String theory as a universal language

Some new results and new speculations on various topics are submitted. They include discussion of open strings in the AdS space, unusual features of D branes, and conformal gauge theories in higher dimensions. The infrared screening of the cosmological constant and the “brane worlds” are also discussed.     

Effects of time delay and non-Gaussian noise on the dynamics of a perceptual bistability

In this paper, we investigate the effects of time delay and non-Gaussian noise on the dynamics properties of the attractor network model of perceptual bistability. Using delay Fokker–Planck equation and projection operator method, the stationary probability distribution P_st(x), the associated relaxation time T_c, and the normalized correlation function C(s) for perceptual bistability are obtained, respectively. Research results show that: (i) the time delay τ and the correlation time τ₀ from non-Gaussian noise can induce the change of the peaks in the P_st(x), i.e., the transition of the system appears; (ii) there exhibits an optimal value of the τ₀ or τ by which the T_c or C(s) is maximum, this maximum shows the τ₀ or τ first reduces the stability of the attractor network model of perceptual bistability in the steady state, and then enhances it; and (iii) the noise intensity P or departure q from the Gaussian noise only enhances the stability of the attractor network model of perceptual bistability in the steady state.     

The time course of acoustic/phonemic cue integration in the sensorineurally hearing-impaired listener

There is limited documentation available on how sensorineurally hearing-impaired listeners use the various sources of phonemic information that are known to be distributed across time in the speech waveform. In this investigation, a group of normally hearing listeners and a group of sensorineurally hearing-impaired listeners (with and without the benefit of amplification) identified various consonant and vowel productions that had been systematically varied in duration. The consonants (presented in a /haCa/ environment) and the vowels (presented in a /bVd/ environment) were truncated in steps to eliminate various segments from the end of the stimulus. The results indicated that normally hearing listeners could extract more phonemic information, especially cues to consonant place, from the earlier occurring portions of the stimulus waveforms than could the hearing-impaired listeners. The use of amplification partially decreased the performance differences between the normally hearing listeners and the unaided hearing-impaired listeners. The results are relevant to current models of normal speech perception that emphasize the need for the listener to make phonemic identifications as quickly as possible.