Volume 112, Issue 5, November 2002
Index of content:
- SPEECH PERCEPTION 
Spectral and temporal cues to pitch in noise-excited vocoder simulations of continuous-interleaved-sampling cochlear implants112(2002); http://dx.doi.org/10.1121/1.1506688View Description Hide Description
Four-band and single-band noise-excited vocoders were used in acoustic simulations to investigate spectral and temporal cues to melodicpitch in the output of a cochlear implantspeech processor. Noise carriers were modulated by amplitude envelopes extracted by half-wave rectification and low-pass filtering at 32 or 400 Hz. The four-band, but not the single-band processors, may preserve spectral correlates of fundamental frequency Envelope smoothing at 400 Hz preserves temporal correlates of which are eliminated with 32-Hz smoothing. Inputs to the processors were sawtooth frequency glides, in which spectral variation is completely determined by or synthetic diphthongal vowel glides, whose spectral shape is dominated by varying formant resonances. Normal listeners labeled the direction of pitch movement of the processed stimuli. For processed sawtooth waves, purely temporal cues led to decreasing performance with increasing With purely spectral cues, performance was above chance despite the limited spectral resolution of the processors. For processed diphthongs, performance with purely spectral cues was at chance, showing that spectral envelope changes due to formant movement obscured spectral cues to Performance with temporal cues was poorer for diphthongs than for sawtooths, with very limited discrimination at higher These data suggest that, for speech signals through a typical cochlear implant processor, spectral cues to pitch are likely to have limited utility, while temporal envelope cues may be useful only at low
Investigating alternative forms of clear speech: The effects of speaking rate and speaking mode on intelligibility112(2002); http://dx.doi.org/10.1121/1.1509432View Description Hide Description
Sentences spoken “clearly” (and slowly) are significantly more intelligible than those spoken “conversationally” for hearing-impaired listeners in a variety of backgrounds [Picheny, Durlach, and Braida, J. Speech Hear. Res. 28, 96–103 (1985); Uchanski et al., J. Speech Hear. Res. 39, 494–509 (1996); Payton, Uchanski, and Braida, J. Acoust. Soc. Am. 95, 1581–1592 (1994)]. However, it is unknown whether slower speaking rates are necessary for highly intelligible speech or whether an alternative form of clear speech exists at faster (i.e., normal) rates. To investigate this question, talkers with significant public speaking experience were asked to produce clear and conversational speech at slow, normal, and quick rates. A method for eliciting clear speech was introduced that ensured the clearest possible speech was obtained at each of these speaking rates. To probe for other highly intelligible speaking modes, talkers also recorded sentences in two other speaking modes: soft and loud. Intelligibility tests indicated that clear speech was the only speaking mode that provided a consistent intelligibility advantage over conversational speech. Moreover, the advantage of clear speech was extended to faster speaking rates than previously reported. These results suggest that clear speech has some inherent acoustic properties that contribute to its high intelligibility without altering rate. Identifying these acoustic properties could lead to improved signal-processing schemes for hearing aids.