Volume 125, Issue 1, January 2009
Index of content:
- SPEECH PERCEPTION 
The contribution of temporal fine structure to the intelligibility of speech in steady and modulated noise125(2009); http://dx.doi.org/10.1121/1.3037233View Description Hide Description
Speech reception thresholds were measured with steady and amplitude-modulated noise maskers for signals processed to contain variable amounts of temporal fine structure (TFS) information. Subjects benefited more from TFS information for the modulated than for the steady masker. For both maskers, addition of TFS information up to improved performance, though the improvement was greater for the modulated masker. The addition of TFS information at higher frequencies improved performance further for the modulated masker only. These results are consistent with the idea that TFS information is important for listening in the dips of a fluctuating masker.
125(2009); http://dx.doi.org/10.1121/1.3035837View Description Hide Description
Three experiments were conducted using the TVM sentences, a new set of stimuli for competing speech research. These open-set sentences incorporate a cue name that allows the experimenter to direct the listener’s attention to a target sentence. The first experiment compared the relative efficacy of directing the listener’s attention to the cue name versus instructing the subject to listen for a particular talker’s voice. Results demonstrated that listeners could use either cue about equally well to find the target sentence. Experiment 2 was designed to determine whether differences in intelligibility among talkers’ voices that were noted when three utterances were presented together persisted when each talker’s sentences were presented in steady-state noise. Results of experiment 2 showed only minor intelligibility differences between talkers’ utterances presented in noise. The final experiment considered how providing accurate and inaccurate information about the target talker’s voice influenced speech recognition performance. This voice cue was found to have minimal effect on listeners’ ability to understand the target utterance or ignore a masking voice.
Masking release for low- and high-pass-filtered speech in the presence of noise and single-talker interference125(2009); http://dx.doi.org/10.1121/1.3021299View Description Hide Description
Speech intelligibility was measured for sentences presented in spectrally matched steady noise, single-talker interference, or speech-modulated noise. The stimuli were unfiltered or were low-pass (LP) ( cutoff) or high-pass (HP) ( cutoff) filtered. The cutoff frequencies were selected to produce equal performance in both LP and HP conditions in steady noise and to limit access to the temporal fine structure of resolved harmonics in the HP conditions. Masking release, or the improvement in performance between the steady noise and single-talker interference, was substantial with no filtering. Under LP and HP filtering, masking release was roughly equal but was much less than in unfiltered conditions. When the average of the interferer was shifted lower than that of the target, similar increases in masking release were observed under LP and HP filtering. Similar LP and HP results were also obtained for the speech-modulated-noise masker. The findings are not consistent with the idea that pitch conveyed by the temporal fine structure of low-order harmonics plays a crucial role in masking release. Instead, any reduction in speech redundancy, or manipulation that increases the target-to-masker ratio necessary for intelligibility to beyond around , may result in reduced masking release.
English /r/-/l/ category assimilation by Japanese adults: Individual differences and the link to identification accuracy125(2009); http://dx.doi.org/10.1121/1.3021295View Description Hide Description
Native speakers of Japanese often have difficulty identifying English /r/ and /l/, and it has been thought that second-language (L2) learning difficulties like this are caused by how L2 phonemes are assimilated into ones native phonological system. This study took an individual difference approach to examining this relationship by testing the category assimilation of Japanese speakers with a wide range of English /r/-/l/ identification abilities. All Japanese subjects were assessed in terms of (1) their accuracy in identifying English /r/ and /l/, (2) their assimilation of /r/ and /l/ into their Japanese flap category, (3) their production of /r/ and /l/, and (4) their best-exemplar locations for /r/, /l/, and Japanese flap in a five-dimensional set of synthetic stimuli (F1, F2, F3, closure duration, and transition duration). The results demonstrated that Japanese speakers assimilate /l/ into their flap category more strongly than they assimilate /r/. However, there was little evidence that category assimilation was predictive of English /r/-/l/ perception and production. Japanese speakers had three distinct best exemplars for /r/, /l/, and flap, and only their representation of F3 in /r/ and /l/ was predictive of identification ability.