1. Department of Audiology, Tohoku University Graduate School of Medicine, Sendai, Japan
2. Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan
3. Research Institute of Electrical Communication, Tohoku University, Sendai, Japan
4. Laboratory of Rehabilitative Auditory Science, Tohoku University Graduate School of Biomedical Engineering, Sendai, Japan