The perception of /shu/ and /shi/ with devoiced vowels included in geminate/non-geminate words by young normal-hearing listeners

Abstract

In this paper, the results of the experiment for young normal-hearing listeners were presented, which is a part of the whole project, the perception experiment for young normal-hearing and elderly listeners. The perception experiment was conducted by using geminate and non-geminate words with /shu/ and /shi/ (referred to as /∫u/ and /∫i/), `shukan,' `shukkan,' `shikan' and `shikkan,' having devoiced and non-devoiced vowels to investigate if the lower limit frequency (F_L) and its falling affect to discriminate /∫u/ from /∫i/ with devoiced vowels by young normal-hearing listeners. The synthesised fricative sound was used for C₁, and the frication has three types of F_L, 1,440 Hz, 2,760 Hz and 4,080 Hz. Moreover, there are two patterns of the frication with each F_L: 1) F_L of the frication was kept in the same frequency until the end of the frication in each F_L, and 2) the frequencies fall from each F_L to 480 Hz in the middle of the frication. The rate which they perceive as /∫u/ (referred to as the response rate of /∫u/) for stimuli with devoiced vowels in F_L falling condition was higher than in F_L non-falling condition. The response rates of /∫u/ in the both devoiced/non-devoiced condition were also higher in case that the F_L was 1,440 Hz regardless of F_L falling. Hence, these results implied that F_L itself and F_L falling affect to distinguish /∫u/ from /∫i/ with devoiced vowels by young normal-hearing listeners. In the results of geminate perception, the tendency was observed that the response rates of geminate for the stimuli with devoiced vowels were almost same as the response rates for the stimuli with non-devoiced vowels, suggesting it was possible for young normal-hearing listeners to discriminate geminate from non-geminate even when vowels were devoiced.