Because ultrasound is a sound wave with a frequency higher than 20,000 Hz, and the frequency range of sound that humans can hear is 20hz ~ 20000Hz, people can't hear it, and bats have extremely developed hearing and can be located by ultrasound.

Usually bats have poor eyesight, but their hearing is extremely developed. At night or in a very dark environment, they can fly freely and catch food accurately.

70% bat species mainly feed on insects and other small arthropods; Other species mainly feed on fruits, nectar and pollen; Some tropical species are carnivores, and three vampire bats feed on blood. Distributed in all parts of the earth except the north and south poles and some ocean islands.

Extended data:

Living habits of bats

Bats have adapted to the ability of flying and living at night, and their physiological functions have undergone a series of important changes. Usually bats have poor eyesight, but their hearing is extremely developed. At night or in a very dark environment, they can fly freely and catch food accurately. The most basic means is to use echolocation.

Experiments show that most bats use ultrasonic pulses from their throats to locate themselves. But this is different. Some large fruit bats, such as brown fruit bats, have special echolocation ability. They use the sound of licking their tongues as the basis for sound location.