In this paper, we describe a robotic spatial sound localization system using an auditory interface with four microphones arranged on the surface of a spherical robot head. The time difference and intensity difference from a sound source to different microphones are analyzed by measuring the HRTFs around the spherical head in an anechoic chamber. It was found while the time difference can be approximated by a simple equation, the intensity difference is more complicated for different azimuth, elevation and frequency. A time difference based sound localization method was proposed and was tested by experiments.A sound interface for human listeners is also constructed by four loudspeakers with similar arrangement as the microphone set. This interface can be used as 3-D sound human interface by passing the four channel audio signals from the microphone set directly to the four loudspeakers. It can also be used to create 3-D sound with arbitrary spatial position which is determined by a virtual sound image or by the sound localization system.