Most bats use sound or biological sonar, known as echolocation, to navigate. Bats emit sounds that bounce back like an echo and allow them to detect obstacles in their path, locate roosts and find food.
There are more than 900 species of bats, and most of them use various physical features, such as megaphone-like ears and sonar, as their primary guidance mechanism. Bats use their voices, their nostrils or their tongues to emit ultrasonic sounds in the frequency range of 20 to 200 kilohertz (Khz). Humans can't hear bats' sounds because human hearing peaks at about 20 Khz. It is a loud sound ranging from 50 to 120 decibels, which would be like a smoke alarm going off about 4 inches from your ear.
Scientific American magazine reports that echolocation calls are characterized by intensity (decibel level), frequency and how long they last. Most bats use a combination of low- and high-frequency echolocation sounds to tell them the size, range, position, speed and direction of a prey's flight. The brains and ears of a bat are extremely sensitive to frequency change and can zero in on an insect one meter away in about six milliseconds. The various sizes, shapes, folds and wrinkles in the ears of bats are believed to be an important part of a bat's ability to detect and zero in on prey.