![]() ![]() Yet although these calls are some of the loudest ever recorded in the animal kingdom, they are inaudible to us. Simpler forms of echolocation are also used by cave swiftlets and oil birds, nocturnal shrews and rats they, too, see the world through sound. Biosonar (as echolocation is also known) functions somewhat like an acoustic flashlight, honed by evolution to be as accurate as our finest medical devices. By using what is known as echolocation, bats and toothed whales create images of their surroundings by sending out beams of ultrasound and analyzing the returning echoes. Still other species use ultrasound to visualize their world: to navigate, find mates, and follow prey. Related Article Read ‘The Sounds Of Life’ With The SciFri Book Club But contemporary humans have lost this ability. Our ancestors may once have been able to hear these high-pitched sounds, and our smaller primate cousins-tiny tarsiers and dwarf lemurs-can still communicate in ultrasound. A surprisingly diverse array of species-mice and moths, bats and beetles, corn and corals-emit ultrasonic sounds imperceptible to humans. At best, we can sometimes sense infrasound as a throbbing in the chest, or a troubling feeling of unease.Īt the other end of the spectrum, above the upper threshold of human hearing, lies the ultrasonic: high-frequency sounds that vibrate too quickly for us to hear. Our hearing is typically confined to a relatively narrow band of frequencies, between 20 Hz and 20 kHz, a range that narrows as we age. Many animals-rock doves and snakes, tigers and mountain beavers-are able to hear these low-frequency sounds, but not humans. The planet’s infrasonic chorus is continuously sounding all around you. When earthquakes convulse our planet’s surface, they create airborne infrasonic tremors-ringing our atmosphere like a quiet bell. As ocean waves collide over continental shelves, they vibrate the Earth’s crust in a rhythmic fashion-the drumming heartbeat of our planet. Lowest of all, the Earth’s periodic infrasonic pulse resonates below our feet and through the air. If you could tune into the Earth’s infrasound, you might hear the rumblings of calving icebergs, the howl of a volcano, or the roar of a typhoon halfway around the world. ![]() The deepest infrasound is generated by our planet itself. In one of the animal kingdom’s most famous mating rituals, male peacocks transmit powerful infrasound with their raised tails what humans perceive to be a visual display is, in fact, a sonic summons. ![]() Many creatures can sense and communicate in infrasound, which travels long distances with ease, passing through air and water, soil and stone. Below the lower end of human hearing lies deep infrasound: the realm of thunder and tornadoes, elephants and whales. Compared with our cousins on the Tree of Life, humans are poor listeners. ![]()
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