An inquiry into the relation between the speech style and the speech production of learners of Japanese as a second language

众所周知，日语长元音对于作为第二语言的日语学习者来说是很困难的，日语教科书中经常会出现“倍长”、“两拍”之类的表述。然而，在实际语音中，一些长元音的长度被缩短，听起来像短元音。本研究采用三种不同的研究方法对长元音缩短现象进行了初步研究：首先，我们对母语为英语的人朗读卡片上句子的录音进行了分析，发现没有出现长元音缩短现象。然后，我们分析了一段自发对话的录音，发现长元音缩短在非词首位置比在词首位置更有可能发生。最后，我们准备了元音长度控制在十个阶段的合成句子，并进行了范畴知觉测试。结果表明，母语为日语的人在非词首位置的元音缩短感低于在词首位置的元音缩短感。

It is well known that Japanese long vowels are difficult for learners of Japanese as a second language, Expressions like "double-length", "two beats" or the like are found in Japanese textbooks. In actual speech, however, length of some long vowels is shortened and they sound like short vowels. In this resarch, we describe preliminary research of the long-vowel-shortening phenomena which was carried out using three different research methods.First, we analyzed acoustically recordings of native speakers reading sentences written on cards and found that long-vowel-shortening did not occur. Then we analyzed a recording of spontaneous conversation and found out that long-vowel-shortening was more likely to occur at non-word-initial positions than at word-initial-positions. Lastly we prepared synthesized sentences in which vowel length was controlled in ten stages and carried out a categorical perception test. The results indicated that native speakers of Japanese have less keen sense of vowel shortening at non-word-initial positions than at word-initial positions.