The Frequency Below Hearing
A tiger's roar peaks at around 18 Hz, just below the threshold of human hearing, which begins at 20 Hz. That gap is not a flaw in the tiger's design. It is the design. Infrasound at 18 Hz does not enter the ear cleanly the way a car horn does. It moves through the body as a pressure wave, absorbed by soft tissue, organs, and the fluid in the inner ear simultaneously. The result is a sensation that arrives before conscious perception, a dread the brain cannot locate or explain.
