Human characteristics of sound localization under masking for the early detection of dementia

Sound localization ability differs among people, such as between a young person, a senior citizen, and a dementia patient. Therefore, it is possible to detect dementia at an early stage by measuring a difference in this ability. Experiments for sound source localization in the horizontal plane show that the ability is improved by separating the presented locations between the signal and a masker. However, there are few data regarding sound localization in the vertical plane. The threshold in the perpendicular plane has been measured, but only experiments in the median plane regarding sound localization have been reported, and its characterization in other aspects has not been clarified. Previous studies about localization ability in the vertical plane have reported contradictory results. One is that the sound source from an upper direction is perceptually superior for a subject, and the other is that a lower direction is superior. The purpose of this study in this chapter is to clarify sound localization ability in the vertical plane and to detect dementia in the early stage using the aging tendency of aural characteristics.