Exploring dolphin spatial hearing in ocean ambient soundscape via model head-related transfer functions

The ocean ambient soundscape is a dynamic mixture of natural and anthropogenic acoustic signals. As fully aquatic mammals, dolphins rely primarily on acoustic cues—from pure listening and echolocation—to navigate, communicate, and forage. Spatial hearing, the ability to localize sound sources, is central to how dolphins interpret and negotiate rich underwater acoustic scenes. Here, we explore dolphins′ spatial hearing capabilities using head-related transfer functions (HRTFs) predicted from finite element modeling using a 3-D volumetric representation of a dolphin head. The HRTF predictions revealed a distinct transition of hearing directionality around 15–20 kHz: Broad, lateralized patterns dominate the lower communication band, while highly directional, frontally oriented patterns appear in higher echolocation frequencies. These features arise from the unique anatomical structures in the dolphin head, including mandibular fat bodies that refract and guide sound toward the ears, and extensive air spaces around the ears and beneath the skull that acoustically isolate each ear from contralateral sources. Results suggest that dolphins can effectively localize environmental sounds and achieve high spatial acuity during echolocation despite long acoustic wavelengths of audible underwater sound. Our study offers fresh perspectives on dolphin acoustic ecology and provides a foundation to assess the potential impacts of anthropogenic sounds in the ocean.