3/2方式によるトランスオーラル技術の先行研究で音像定位精度が検討されているが，その中で音像定位の正答率に10％と90％という違いが見受けられた．この一つの原因として，試験環境が遮音室と無響室であったため，反射波の影響が考えられる．本報告では，仮想音源に含まれる反射波成分の影響における苦像定位精度の検討を目的とし，含まれる反射波成分が直接波のみ，第1反射波まで，第2反射波まで，第3反射波までの4種類の仮想音源を作成し，音像の定位とシャープネスについて受聴試験を行った．その結果，全方位で，前後誤判定率，平均定位誤差について仮想音源に含まれる反射波成分との関係は一意的ではなかった．一方，シャープネスは，全方位において直接波のみの仮想音源が有意水準5％で最も高かった．%High-quality sound services are being provided by DVD and digital terrestrial broadcasting systems. A common sound reproduction system is the 3/2 loudspeaker arrangement, and many papers on this arrangement have been presented. The accuracy of sound image localization has been discussed, but there are differences (10% and 90%) in the correct answer rates reported in past papers. It is thought that the reflected waves in the room might be one reason for this. This paper describes a study on the effect of reflected waves on the accuracy of sound image localization. In order to study the effect of the reflected waves, the impulse response is separated into four time periods: the direct wave, up to the 1st reflected wave, up to the 2nd reflected wave, up to the 3rd reflected wave. SRTF is calculated for each period. Listening tests to evaluate the perceived direction and sound image sharpness were carried out. The results of perceived direction evaluation tests indicated that the averaged localization error and Front-Back confusion rate don't depend on the reflected waves in the four periods. A test of sound image sharpness showed that the direct wave component offered the highest value all-round, its significance level was 5%.
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