Index of content:
Volume 116, Issue 4, October 2004
- SPEECH PERCEPTION 
116(2004); http://dx.doi.org/10.1121/1.1787528View Description Hide Description
When instructed to speak clearly for people with hearing loss, a talker can effectively enhance the intelligibility of his/her speech by producing “clear” speech. We analyzed global acoustic properties of clear and conversational speech from two talkers and measured their speech intelligibility over a wide range of signal-to-noise ratios in acoustic and electric hearing. Consistent with previous studies, we found that clear speech had a slower overall rate, higher temporal amplitude modulations, and also produced higher intelligibility than conversational speech. To delineate the role of temporal amplitude modulations in clear speech, we extracted the temporal envelope from a number of frequency bands and replaced speech fine-structure with noise fine-structure to simulate cochlear implants. Although both simulated and actual cochlear-implant listeners required higher signal-to-noise ratios to achieve normal performance, a 3–4 dB difference in speech reception threshold was preserved between clear and conversational speech for all experimental conditions. These results suggest that while temporal fine structure is important for speech recognition in noise in general, the temporal envelope carries acoustic cues that contribute to the clear speech intelligibility advantage.
Training native English speakers to perceive Japanese length contrasts in word versus sentence contexts116(2004); http://dx.doi.org/10.1121/1.1783351View Description Hide Description
This study investigated whether native speakers of American English with no knowledge of Japanese could learn to perceive Japanese vowel and consonant length distinctions through auditory training with immediate feedback. One group of participants was trained to identify the number of moras in Japanese words spoken in isolation (word training), and another group in sentences (sentence training). Trained groups’ pretest and post-test scores in the words-in-isolation context (word context) and the words-in-sentences context (sentence context) were compared to those of an untrained control group. The questions addressed were whether there was an overall effect of training, and whether there were differential effects of two types of training. Both trained groups showed similar improvement in their overall test scores. The results suggested that learning in one context generalized to the other. However, an advantage of sentence training over word training was found: at the post-test, there was a greater difference between the scores of the two contexts for the word-training group than for the sentence-training group. The results are discussed in terms of the factors that might contribute to the differences in second language learning between the word and the sentence contexts.
Development of a quick speech-in-noise test for measuring signal-to-noise ratio loss in normal-hearing and hearing-impaired listeners116(2004); http://dx.doi.org/10.1121/1.1784440View Description Hide Description
This paper describes a shortened and improved version of the Speech in Noise (SIN™) Test (Etymotic Research, 1993). In the first two of four experiments, the level of a female talker relative to that of four-talker babble was adjusted sentence by sentence to produce 50% correct scores for normal-hearing subjects. In the second two experiments, those sentences-in-babble that produced either lack of equivalence or high across-subject variability in scores were discarded. These experiments produced 12 equivalent lists, each containing six sentences, with one sentence at each adjusted signal-to-noise ratio of 25, 20, 15, 10, 5, and 0 dB. Six additional lists were also made equivalent when the scores of particular pairs were averaged. The final lists comprise the “QuickSIN” test that measures the SNR a listener requires to understand 50% of key words in sentences in a background of babble. The standard deviation of single-list scores is 1.4 dB SNR for hearing-impaired subjects, based on test-retest data. A single QuickSIN list takes approximately one minute to administer and provides an estimate of SNR loss accurate to at the 95% confidence level.