Infrasounds are prevalent among creatures in nature, too. Hippopotamuses, alligators, and giraffes reportedly use infrasound to communicate over distances—perhaps hundreds of miles in the case of whales and elephants. Sumatran Rhinoceros produce infrasounds as low as 3 Hz with similarities to the song of the humpback whale. Recent research by Jon Hagstrum of the US Geological Survey suggests that homing pigeons use low frequency infrasound to navigate. Elephants trumpet at 15-35 Hz and as loud as 117 decibels, the sound traveling distances up to six miles and used to coordinate the movement of herds and allow mating elephants to find each other. Elephants also produce infrasound waves that travel through solid ground and are sensed by other herds using their feet, although separated by hundreds of miles. Typically, you can feel and hear your cat purr because the purr of felines is reported to cover a range of 20 Hz to 50 Hz. And then there is the roar of the tiger. More on that tomorrow.