Animals and ultrasound

Many animals hear, and use, sounds outside our hearing range.

Elephants

Elephants, with their large ears, hear very low-frequency sounds — infrasound below 20 Hz.

Rabbits, dolphins, bats

These animals hear ultrasound above 20 000 Hz.

Dogs

Dogs hear ultrasound up to about 40 000 Hz.

Bats find their way with echoes

Bats fly at night by giving out ultrasound as they go. The waves bounce off obstacles ahead and come back; by picking up the reflected waves the bat works out where the obstacles are, and flies around them.

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Figure 4.34 — a bat sending out ultrasound towards a moth, and the waves reflecting back to it.

Dolphins use ultrasound to find small fish to eat and to detect sharks that might attack them. They also use it to communicate with one another.

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Figure 4.35 — dolphins hunting among a shoal of fish.