The skull is a low-frequency external ear in mysticetes! This contribution makes that statement precise, visualizes it with finite-element modeling, and validates it with carefully controlled vibroacoustic experiments on gray whale skulls. The authors synthesize anatomy, modeling, and empirical data to show how incident low-frequency (LF) underwater sound energy feeds into whole-skull vibration, which is then mechanically amplified by the tympanoperiotic complex (TPC) to drive the ossicular chain and cochlea. The multiyear effort converts a long-standing hypothesis of bone conduction in mysticetes into an experimentally grounded mechanism with far-reaching ecological, natural history, and management implications.