A new method for measurement of word intelligibility under noisy and reverberant environment in a short duration

Word/sentence intelligibility tests is advantageous over nonsense monosyllable test in the presence of noise and reverberation. This is because the effect of noise and reverberation to the speech understanding can be analyzed. However, to measure speech hearing ability under living environments with various noise and reverberation, it is needed to prepare a lot of word/sentence lists because learning effect may strongly affects the results of these tests. In this paper, we introduce our new word intelligibility test to measure, with a short duration, speech recognition threshold (SRT) as the index of speech hearing ability under various acoustical conditions with noise and reverberation. In the method, we first estimate listener's initial SRT by using their audiograms or only by their ages. Speech materials are then presented at the sound pressure levels around the estimated SRT. A closed-set consisted of a test word and five alternative words. Two of five alternative words were phonetically-similar-words in where only one consonant is different from the test word. Other three alternative words were randomly-selected distracters which were not phonetically similar to the test word. By presenting the speech materials a couple of times, SRT is calculated as the 50 % point of psychometric function. The results indicated that approximate SRT can be obtained by using proposed method. Moreover, experimental duration of the method was about one-third shorter than that of traditional methods. We will further examine the learning effect of the proposed method because this method is expected to be with small learning effect.