The call that comes back as a map
A bat leaving its roost at dusk emits ultrasound pulses at frequencies between 20 and 200 kilohertz, well above the ceiling of human hearing, which tops out around 20 kHz. Each pulse lasts between 0.2 and 100 milliseconds. The echo that bounces back carries the distance, size, texture, and velocity of every object in the bat's path. The bat's brain resolves all of this into a working spatial map before the next pulse fires.
