Bio-inspired sonar antennae: Enhancing directivity patterns for localization

We present results of a biologically inspired method to enhance a sonar transducerpsilas directivity pattern for localization purposes. We show that an artificial pinna structure mounted over a transducer introduces features in its head related transfer function that are more interesting for localization than those in the basic piston-like directivity pattern of common ultrasonic transducers. We measured the directivity pattern of several transducer-pinna assemblies using a biologically inspired robotic bat head. We compare the measured head related transfer function of a larger (Oslash 10 mm) electromechanical film sensor with that of a much smaller commercially available electret condenser microphone, both with and without pinna. We investigate the added spatial filtering of a tragus or a ripple pattern in the pinna structure. We build monaural elevation template sets from the measured head related transfer functions and use an intertemplate distance metric to show that mounting a pinna structure over the receiving transducers makes these templates more suitable for localization.