Perceptual Study on the Effects of Language Transfer on the Naturalness of Japanese Prosody for Isolated Words

Many Japanese language learners have a desire to learn how to speak natural sounding Japanese. Despite this, due to language transfer, they might find it difficult to attain this goal. The errors that occur due to language transfer can vary widely from first language to first language. In this paper, we look at what kinds of accents cause the greatest loss in naturalness in terms of pronunciation. Here, we focus on prosodic errors at the lexical level. For this, we constructed a balanced speech database emphasizing number of mora, accent type, and the existence of heavy syllables, recording the speech of individuals who can pronounce both Japanese and another language (English, Chinese, and Korean) at a native level. For each word, we had each individual produce the word in the Tokyo Japanese Dialect and the foreign accent of the other language that they speak. For the present analysis, we used STRAIGHT to morph the native Japanese speech into the accented speech for a variety of parameters. Through this process we were able to obtain speech at various levels between the accented speech and native speech for each parameter. We had native Japanese speakers evaluate the morphed samples as well as the native samples, and inspected the results of the evaluation.