Beneath the ocean's surface, where noise pollution grows louder with each passing decade, researchers have begun mapping the inner acoustic lives of seals, sea lions, and walruses — asking not merely whether these animals can hear, but how well they can listen. A study measuring critical bandwidth across four pinnipeds reveals that seals possess a specialized capacity to filter low-frequency signals from noise, a gift that carries within it a quiet vulnerability: the very frequencies they hear best are the ones that threaten them most.