# Effects of Visually Induced Self-Motion on Sound Localization Accuracy
## 1 Introduction  
The influence of visual, proprioceptive, and vestibular systems on sound localization has been investigated in various studies [1; 2; 3; 4; 5; 6; 7; 8], including a good review to overview this issue [2]. For instance, [PERSON] [7] reported that sound-source localization requires an interaction of auditory-spatial and head-position cues. His study revealed that the construct of auditory space is dependent upon self-motion; despite movement of the head, listeners can perceive a stable auditory environment and use it to accurately localize sounds [7; 9]. These evidences [1; 2; 3; 4; 5; 6; 7; 8] demonstrate that sound localization is a multisensory integration process involving self-motion [10; 11]. In fact, previous studies have demonstrated that a listener's head/body movement facilitates sound localization by leveraging dynamic changes in the information input into the ears [10; 11; 12; 13; 14; 15; 16; 17; 18]. However, recent reports have shown that sound localization accuracy deteriorates during rotation of the listener's head/body [19; 20; 21; 22; 23]. Thus, the effects of self-motion on sound localization accuracy remain a topic of debate. In this context, it has been confirmed that the deterioration of sound localization accuracy is independent of the listener's rotation velocity [21; 22; 23]. For instance, [PERSON] et al. [23] reported that sound-localization resolution degrades with passive rotation, irrespective of the rotation speed, even for very low speeds of 0.625\({}^{\circ}\)/s. Their results suggest that the deterioration of sound localization accuracy is almost independent of bottom-up effects,such as ear-input blurring. A more appropriate explanation for the deterioration is in terms of the listeners' perception of self-motion. The visual system plays a vital role in self-motion perception. For instance, visually induced self-motion perception can be generated by presenting large optic flow patterns to physically stationary observers [24]. This perceptual phenomenon is often referred to as vection. Several studies have investigated the effects of visually induced self-motion on sound localization. The results of [PERSON]'s classical study [7] suggest that vection leads to the same performance in sound-source localization for moving and stationary sounds as actual self-motion. Recently, [PERSON] et al. [25] reported that the auditory space is distorted during visually induced self-motion in depth. They presented a large-field visual motion to induce self-motion perception in participants and investigated whether this linear self-motion information can alter auditory space perception. During the participants' experience of self-motion, a short noise burst was delivered from one of the spatially distributed loudspeakers on the coronal plane. The participants were asked to indicate the position of the sound (forward or backward) relative to their coronal plane. The results showed that the sound position aligned with the subjective coronal plane was significantly displaced in the direction of self-motion. Their findings [7,25] indicate that self-motion information, irrespective of its origin, is crucial for auditory space perception. If the perception of self-motion itself, induced by any information, is crucial for auditory space perception [7,25], sound localization accuracy would deteriorate not only during actual self-motion [19, 20, 21, 22, 23] but also in the event of self-motion perception. In visually induced self-motion, the input difference between the two ears remains constant because the listener does not perform any head/body movement. Therefore, if the deterioration is also observed during self-motion perception, the findings of [PERSON] [7] and [PERSON] et al. [25] would support the idea that self-motion information is crucial for auditory space perception. In this study, our main aim was to investigate how self-motion information affects sound localization in detail when listeners perceive rotational self-motion.