Various high-fidelity VAD systems are developed for many practical application fields including games, home theatre, virtual reality, and military simulator, etc. Head-related Transfer Function is the one of key functions widely used in VAD system. We developed robot auditory systems for sound source localization to achieve the effective human-robot interaction. The developed robot auditory system, which includes artificial ear, MEMS sensor, SoC (system-on-chips) for sound localization can be used for intelligent robots to process speech/acoustic signals.