Hardware and software technologies for improvement of hearing characteristics of headphone reproduction

Abstract

This report specifically describes commercialization technology of a headphone system with out-of-head localization applying dynamic head-related transfer functions (HRTFs) that can localize sound easily over a full 360 deg. A source image by output of conventional headphones is localized inside the listener’s head. However, the image can be localized outside the listener’s head by wearing headphones over a full 360 deg through accurate simulation of the listener’s HRTFs. Developments of headphone systems using signal processing technology for data correction have given rise to the static binaural reproduction system (SBRS). The first part of this speech describes its psychoacoustic characteristics and challenges. A rotating dummy-head that is synchronized with the listener’s head movement was produced experimentally to create the dynamic binaural reproduction system (DBRS). Using the DBRS, HRTFs synchronize with the listener’s head movement. Psychoacoustic characteristics and advantages of the system are also discussed in this report. Further developments were made to realize the commercialization of the DBRS in areas including piezoelectric gyroscope head-tracking technology, headphone technologies that can reproduce real sound characteristics, and simplification of HRTF signal processing employing a simulator with electronic circuits. Finally, future visions for these technologies will be touched upon.