音像定位を利用した単一振動子による運指表現手法の提案

楽器演奏時の運指を振動刺激で表現する場合，各指に振動刺激を提示するために，複数の振動子を搭載した専用触覚デバイスが必要となる．そこで，本研究では，単一振動子を複数の指で把持したときに，特定の指にのみ振動が提示されていると錯覚させることで運指を表現する手法を提案する．本手法では，触覚と聴覚のクロスモーダル知覚に着目し，音の定位を左右に変化させることで，それぞれ異なる指で振動を感じているように錯覚させる．被験者10名で実施した実験では，単一振動子を2本または3本の指で把持した状態で音の定位を変化させると，音の定位に応じて振動を知覚する指が変化することが明らかになった．さらに，本手法を運指表現へ適用するための基礎検討を実施したところ，限られたピアノの演奏フレーズにおいて，振動を知覚した指と実際の運指に一定の類似性があることが確認できた．したがって，単一振動子のみを用いた振動刺激でも，本手法によって，運指を表現できる可能性が示された．

Haptic devices equipping multiple vibration transducers enable music experiences to be richer by providing vibration synchronized with music to emphasize rhythms or teach fingering. However, it is not easy for users to experience it because most commercial devices contain only one or two vibration transducers. In this paper, we propose to control multi-finger allocation of vibrotactile perception with a single vibration transducer by using sound localization of piano sounds, which can present piano fingering. We assume that the perceptual position of vibration depends on the sound localization because of cross-modal perception. In the study with ten participants, we investigated on which fingers they perceived vibration when gripping a single vibration transducer with two or three fingers under multiple auditory stimulus conditions. The experimental results showed that the perceived positions of vibration were changed by sound localization; participants perceived vibration on the thumb and little finger alternatively depending on the sound localization though the vibration was presented on both fingers simultaneously. We also evaluated whether participants felt piano fingering of several short phrases by applying our proposed method to both hands' fingers. The results suggested that our method enabled participants to feel piano fingering just by gripping only one vibration transducer for each hand.