Volume 126, Issue 6, December 2009
Index of content:
- SPEECH PERCEPTION 
The dynamic range of speech, compression, and its effect on the speech reception threshold in stationary and interrupted noise126(2009); http://dx.doi.org/10.1121/1.3257225View Description Hide Description
Changes in the speech reception threshold(SRT) after amplitude compression of speech or speech in noise may be due to changes in the dynamic range of the speech signal. However, current models set up to predict the speech intelligibility consider the dynamic range of speech to be fixed regardless of the type of compression. The present paper describes two experiments with normal-hearing subjects to examine the effect of the dynamic range on the SRT in stationary and interrupted noise after wide dynamic range compression. The dynamic range has been varied by compression or expansion of only the speech signal, leaving the masking noise unaltered, or by compression or expansion of the mixed speech-in-noise signal. The results show that compression affects the SRT, both in a positive or a negative direction, not only due to dynamic range but also due to distortion of the speech signal.
126(2009); http://dx.doi.org/10.1121/1.3250425View Description Hide Description
This study investigated the degree to which two types of reduced auditory signals (cochlear implant simulations) and visual speech cues combined for speech identification. The auditory speech stimuli were filtered to have only amplitude envelope cues or both amplitude envelope and spectral cues and were presented with/without visual speech. In Experiment 1, IEEE sentences were presented in quiet and noise. For in-quiet presentation, speech identification was enhanced by the addition of both spectral and visual speech cues. Due to a ceiling effect, the degree to which these effects combined could not be determined. In noise, these facilitation effects were more marked and were additive. Experiment 2 examined consonant and vowel identification in the context of CVC or VCV syllables presented in noise. For consonants, both spectral and visual speech cues facilitated identification and these effects were additive. For vowels, the effect of combined cues was underadditive, with the effect of spectral cues reduced when presented with visual speech cues. Analysis indicated that without visual speech, spectral cues facilitated the transmission of place information and vowel height, whereas with visual speech, they facilitated lip rounding, with little impact on the transmission of place information.
Effects of electrode separation between speech and noise signals on consonant identification in cochlear implantsa)126(2009); http://dx.doi.org/10.1121/1.3257200View Description Hide Description
The aim of the present study was to examine cochlear implant(CI) users’ perceptual segregation of speech from background noise with differing degrees of electrode separation between speech and noise. Eleven users of the nucleus CIsystem were tested on consonant identification using an experimental processing scheme called “multi-stream processing” in which speech and noise stimuli were processed separately and interleaved. Speech was presented to either ten (every other electrode) or six electrodes (every fourth electrode).Noise was routed to either the same (the “overlapped” condition) or a different set of electrodes (the “interlaced” condition), where speech and noiseelectrodes were separated by one- and two-electrode spacings for ten- and six-electrode presentations, respectively. Results indicated a small but significant improvement in consonant recognition (5%–10%) in the interlaced condition with a two-electrode spacing (approximately 1.1 mm) in two subjects. It appears that the results were influenced by peripheral channel interactions, partially accounting for individual variability. Although the overall effect was small and observed from a small number of subjects, the present study demonstrated that CI users’ performance on segregating the target from the background might be improved if these sounds were presented with sufficient peripheral separation.