Why do many bat echolocation calls have frequencies above human hearing?

Bats utilize high-frequency sounds for echolocation because these frequencies are essential for their sonar system to function effectively. To accurately perceive the nature of objects and detect fine details, the wavelengths of the sound must be small in relation to the dimensions of the target.1

Using these high frequencies allows bats to identify, track, and capture small prey, such as insects, and navigate around obstacles as fine as 0.08 mm in diameter. Furthermore, this high-frequency range is largely outside the spectrum of common environmental noises, which helps the bat avoid interference and resist masking sounds that could otherwise hinder their ability to process echoes. The nervous system and auditory structures of bats, including a specialized protein called prestin, have evolved to be highly sensitive to these specific frequencies, ensuring they can effectively interpret the returning signals necessary for survival.213