Augmented sound-image perception using pre-virtual-leading hypersonic signals with bass frequency envelopes

Recently, stereo audio technologies have been proposed to control sound-image localization based on binaural effects. The precedence effect, which occurs when sounds arrive from different directions with a slight time difference, can let listeners perceive a sound-image in the direction of the first arriving sound. Moreover, hypersonic effect suggests that inaudible high-frequency sounds influence audible sound perception. Considering the potential of ultrasound in sound-image control, we have previously proposed a sound-image augmentation method with ultrasonic signals named pre-virtual-lead signals. In this method, a sound-image is constructed with stereo technology, while the pre-virtual-lead signals are used to provide a virtual perception. The direction perception is augmented because the pre-virtual-lead signals can emphasize the direction of sound-image. The signals are designed as amplitude-modulated ultrasounds, based on the tactile perception of ultrasounds. This method has been demonstrated to be effective in limited conditions, where remains the possibility of improving left-right perception. This paper focuses on envelopes of pre-virtual-lead signals and proposes a sound-image control method using pre-virtual-lead signals with envelope frequencies in bass band. Previously, envelope frequencies were chosen based on vibrotactile sensitivity, but here we experimentally investigate the proper envelope frequencies in bass band considering the effect in auditory.