In those types of robots, attention has in recent years been riveted to active perception of vision and audition. 
In a robot, a perception by a sensor provided for its vision or audition is made active (active perception) when a part of the robot carrying the sensor such as its head part is varied in position or orientation controlled by a driving system so that the sensor follows the movement or instantaneous position of a target to be sensed or perceived. 
Studies have diversely been undertaken for active vision, using an arrangement in which at least a camera as the sensor has its optical axis kept directed towards a target as controlled in position by a driving system and while capturing by performing automatic focusing and zooming in and out relative to the target. 
For active audition or hearing, at least a microphone as the sensor may have its directivity kept directed towards a target as controlled in position by a driving system to collect a sound from the target.  The active audition has been found inconvenient, however, in that while the driving system is actuated, the microphone may come to pick up an motion sound from the driving system and this sound as a relatively loud noise may become mixed with the sound from the target, thereby making it hard to recognize the sound from the target. 
Yet, auditory studies performed in the situation that the driving system is at a halt indicate that especially if the target is moving, it is difficult to effect what is called active audition while having the microphone follow the movement of the target. 
Yet further, the microphone as the auditory means may come to pick out not only the sound from the driving system but also various motion sounds generated within the robot and noises steadily emitted from its inside. 
With these problems taken into account, therefore, it is an object of the present invention to provide an auditory apparatus for a robot which can reliably collect a sound from an external target to effect active perception without being affected by noises produced by interior components of a robot.