Volume 136, Issue 2, August 2014
Index of content:
- SPEECH PERCEPTION 
136(2014); http://dx.doi.org/10.1121/1.4889863View Description Hide Description
This study compared modulation benefit for phoneme recognition obtained by normal-hearing (NH) and aided hearing-impaired (HI) listeners. Consonant and vowel recognition scores were measured using nonsense syllables in the presence of a steady-state noise and four vocoded speech maskers. Vocoded maskers were generated by modulating the steady-state noise, in either one or six frequency channels, with the speech envelope extracted from the speech of either a single talker or a four-talker babble. Aided HI listeners obtained lower consonant recognition scores than NH listeners in all masker conditions. Vowel recognition scores for aided HI listeners were comparable to NH scores, except in the six-channel vocoded masker conditions where they were relatively lower. Analysis using the extended speech intelligibility index developed by Rhebergen, Versfeld, and Dreschler [(2006). J. Acoust. Soc. Am. 120(6), 3988–3997] suggested that the signal-to-noise ratio deficit observed in aided HI listeners was largely due to uncompensated audibility loss. There was no significant difference between modulation masking release obtained by NH and aided HI listeners for both consonant and vowel recognition.
Two-microphone spatial filtering provides speech reception benefits for cochlear implant users in difficult acoustic environments136(2014); http://dx.doi.org/10.1121/1.4887453View Description Hide Description
This article introduces and provides an assessment of a spatial-filtering algorithm based on two closely-spaced (∼1 cm) microphones in a behind-the-ear shell. The evaluated spatial-filtering algorithm used fast (∼10 ms) temporal-spectral analysis to determine the location of incoming sounds and to enhance sounds arriving from straight ahead of the listener. Speech reception thresholds (SRTs) were measured for eight cochlear implant (CI) users using consonant and vowel materials under three processing conditions: An omni-directional response, a dipole-directional response, and the spatial-filtering algorithm. The background noise condition used three simultaneous time-reversed speech signals as interferers located at 90°, 180°, and 270°. Results indicated that the spatial-filtering algorithm can provide speech reception benefits of 5.8 to 10.7 dB SRT compared to an omni-directional response in a reverberant room with multiple noise sources. Given the observed SRT benefits, coupled with an efficient design, the proposed algorithm is promising as a CI noise-reduction solution.
The role of spectro-temporal fine structure cues in lexical-tone discrimination for French and Mandarin listeners136(2014); http://dx.doi.org/10.1121/1.4887444View Description Hide Description
The role of spectro-temporal modulation cues in conveying tonal information for lexical tones was assessed in native-Mandarin and native-French adult listeners using a lexical-tone discrimination task. The fundamental frequency (F0) of Thai tones was either degraded using an 8-band vocoder that reduced fine spectral details and frequency-modulation cues, or extracted and used to modulate the F0 of click trains. Mandarin listeners scored lower than French listeners in the discrimination of vocoded lexical tones. For click trains, Mandarin listeners outperformed French listeners. These preliminary results suggest that the perceptual weight of the fine spectro-temporal modulation cues conveying F0 information is enhanced for adults speaking a tonal language.