Yuan-Chuan Chiang

Onset dominance in lateralization

Saberi and Perrott [Acustica 81, 272-275 (1995)] found that the in-head lateralization of a relatively long-duration pulse train could be controlled by the interaural delay of the single pulse pair that occurs at onset. The present study examined this further, using an acoustic pointer measure of lateralization, with stimulus manipulations designed to determine conditions under which lateralization was consistent with the interaural onset delay. The present stimuli were wideband pulse trains, noise-burst trains, and inharmonic complexes, 250 ms in duration, chosen for the ease with which interaural delays and correlations of select temporal segments of the stimulus could be manipulated. The stimulus factors studied were the periodicity of the ongoing part of the signal as well as the multiplicity and ambiguity of interaural delays. The results, in general, showed that the interaural onset delay controlled lateralization when the steady state binaural cues were relatively weak, either because the spectral components were only sparsely distributed across frequency or because the interaural time delays were ambiguous. Onset dominance can be disrupted by sudden stimulus changes within the train, and several examples of such changes are described. Individual subjects showed strong left-right asymmetries in onset effectiveness. The results have implications for understanding how onset and ongoing interaural delay cues contribute to the location estimates formed by the binaural auditory system.

Spectral and prosodic transformations of hearing-impaired Mandarin speech

This paper studies the combined use of spectral and prosodic conversions to enhance the hearing-impaired Mandarin speech. The analysis-synthesis system is based on a sinusoidal representation of the speech production mechanism. By taking advantage of the tone structure in Mandarin speech, pitch contours are orthogonally transformed and applied within the sinusoidal framework to perform pitch modification. Also proposed is a time-scale modification algorithm that finds accurate alignments between hearing-impaired and normal utterances. Using the alignments, spectral conversion is performed on subsyllabic acoustic units by a continuous probabilistic transform based on a Gaussian mixture model. Results of perceptual evaluation indicate that the proposed system greatly improves the intelligibility and the naturalness of hearing-impaired Mandarin speech.

The effect of background noise on the precedence effect

The current experiment examined the influence of noise on the precedence effect, focusing on the importance of noise source location. Listeners seated in an anechoic chamber judged whether the image produced by a lead‐lag pair of 4‐ms noise bursts (2‐ms delay) was to the left or right of midline. The lag loudspeaker was fixed at 45° to the left or right, while the lead loudspeaker was positioned at a variable number of degrees to the opposite side. The angle of the lead loudspeaker producing 50% judgements favoring the lead was used to estimate its perceptual weighting relative to the lag. This weighting, which was quantified using the c metric developed by Shinn‐Cunningham et al. [ 2923–2932 (1993)], strongly favored the lead when the sounds were presented in quiet. The value of c was reduced markedly when background broadband noise was introduced from 0° or 180° angles, supporting previous findings of a weakened precedence effect in noise. When the background noise source was off‐midline, or lead‐lag pa...

Joint playout and FEC control for multi-stream voice over IP networks

Packet loss and delay are the major network impairments for transporting real-time voice over internet protocol (IP) networks. In the proposed system, multiple descriptions of the speech are used to take advantage of packet path diversity. A new objective method is presented for predicting the perceived quality of multi-stream voice transmission. Also proposed is a joint playout buffer and forward error control (FEC) adjustment scheme that maximizes the perceived speech quality via delay-loss trading. Experimental results showed that the proposed multi-stream voice transmission scheme achieves significant reductions in delay- and packet-loss rates as well as improved speech quality.