Meeting Abstract
Many animals use cues derived from sounds arriving at two ears that are segregated in space to localize sound sources. Animals can also use monoaural cues, such as location based amplitude or spectral profiles, to localize sounds. In mammals these amplitude and frequency responses are thought to be generated by the soft tissue of the pinna, while in barn owls (Tyto alba) they are generated by soft tissue and the facial ruff. Some species, like Northern saw-whet owls (Aegolius acadicus), have not only soft tissue asymmetry, but asymmetry of ear placement in the skull itself. Previously, we used auditory evoked potentials to measure the response of each ear to sound sources placed in different locations around the head. We found that the response at each ear was influenced strongly by the location of the sound source in space. The response amplitude changed most dramatically with elevation and the latency changed most dramatically in the azimuth. Yet, we still know little about the relative contribution of the feathers, soft tissue, and bony morphology to the previously described directional sensitivity. Here we will first discuss the effect of the body, feathers, and skull morphology on the amplitude of sounds recorded with intracranial microphones placed at the tympanum. Then, we will discuss the relative contribution of body, feather and skull-driven sound amplitude differences to directional responses of the auditory nerve, as assessed by auditory evoked potentials.
