Directional Perception in the Human Auditory System

Human perception of auditory direction was tested in the horizontal and mid-sagittal planes. When the auricular funneling and baffling effects are bypassed by extensions of the ear canals, the accuracy of perception worsens significantly. Providing artificial baffling posterior to the extensions of the ear canals improves perception. The accuracy of perception also worsens when the auricular funneling is eliminated by a modeling material filling the conchae while leaving artificial canals for sound entrance. These results indicate that both the auricular funneling and baffling contribute significantly to the anterior versus posterior differentiation. Similarly, the accuracy of superior versus inferior perception is worsened by the modeling material filling the conchae. Prior demonstrations improve the accuracy of perception when the artificial canals created by the modeling material are non-horizontal. However, prior demonstrations do not significantly improve the accuracy of perception when the artificial canals are horizontal. This suggests that the natural slope of the ear canals provides a learnable cue for distinguishing superior versus inferior sounds. The findings can explain why the hearing aids worsen accuracy of directional perception and why the human ear canals are not horizontal.