Identification of sound-localization cues in the HRTF of the bat-head model

Animals such as bats and dolphins exhibit impressive echolocation abilities in terms of ranging, resolution and imaging and therefore represent a valuable learning model for the study of spatial hearing and sound source localization leading to a better understanding of the hearing mechanism and further improvement of the existing localization strategies. This study aims to examine and understand the directional characteristics of a sonar receiver modeled upon the bat auditory system via measurements of the head-related transfer function (HRTF) in the horizontal plane. Four different models of the bat head were considered here and used to evaluate acoustic spectral characteristics of the sound received by the bat's ears – a sphere model, a sphere model with a pinna attached (two pinnae of different size were used in this study) and a bat-head cast. The performed HRTF measurements of the bat-head models were further analyzed and compared to identify monaural spectral localization cues in the horizontal plane defined by the bat's head and pinna shape and size. Our study suggests that the acoustical characteristics of a bio-inspired sonar head measured and specified in advance can potentially improve the performance of a receiver. Moreover, the generated auditory models may hold clues for the design of receiver characteristics in ultrasound imaging and navigation systems.