Augmented sound-image perception using pre-virtual-leading ultrasounds based on precedence effect

In recent decades, stereo technologies have been proposed to control sound images using binaural effects. Among these, some are based on the precedence effect, which is one of binaural effects. This phenomenon can lead the listener to localize the sound image to a direction which is difficult to perceive with other binaural effects, so it can be utilized to augment sound perception in stereo audio. Moreover, emitted ultrasounds have been reported to change the listener’s sensation of the sound, but how ultrasounds influence sound image localization has not been fully considered yet. In this study, we focus on these two facts and propose a sound image augmentation method with the precedence effect caused by ultrasounds. In this method, the sound image is constructed with stereo audible sounds, while the precedence effect is provided by stereo ultrasounds. By utilizing the precedence effect, the perceived direction of a sound image can be augmented, which is difficult with common stereo technologies. In this paper, we define these ultrasounds as pre-virtual-lead signals, as they are emitted before the main audible signals and provide a virtual perception of direction. Moreover, the ultrasounds are inaudible, so they will not affect listening to the contents, such as music and speech. In addition, ultrasounds with low-frequency envelopes are utilized as the precedence effect caused by them is expected to be perceived easily. We conducted subjective evaluation experiments on augmented sound perception by the proposed method and found the proposed method to be effective.