Development of word lists for word intelligibility tests in Japanese

Abstract

Speech intelligibility tests are widely used to evaluate personal speech hearing ability accurately. Although various lists have been proposed for the tests, almost all lists in Japan do not properly consider word difficulty as an aspect of speech recognition. Consequently, even if these tests are performed under identical conditions, correct results cannot be obtained. We have been developing word lists for word intelligibility tests to cope with these problems. We control word familiarity, which strongly affects word recognition scores, to equalize difficulty in recognition between word lists. Words are divided into four word-familiarity ranks. Twenty lists of 50 words are constructed in each rank by considering phonetic balance. Moreover, to compensate slight differences in intelligibility scores among word lists within the same word-familiarity rank, the relationship between the difference of word familiarity and signal-to-noise ratio (SNR) is estimated. Then this relationship is used to compensate the difference of the intelligibility score. The other compensation method is based on speech recognition threshold (SRT). The intelligibility score of each word can be equalized by changing the SNR according to the difference of the SRT of the word. The effectiveness of these compensation methods is discussed.