Why can't humans hear the sounds animals use for echolocation?

Humans can't hear the sounds animals use for echolocation because these sounds typically fall outside the range of human hearing, which is approximately 20 Hz to 20 kHz. Many echolocating animals, like bats and dolphins, produce sounds at ultrasonic frequencies that exceed this range, often above 20 kHz. Additionally, the specific characteristics of these sounds, such as their rapid pulses and high frequencies, may not be perceptible to human ears even within the audible range.