Bats Emit Ultrasonic Sound Waves To Locate Their Prey

Bats use high frequency (low wavelength) ultrasonic waves in order to enhance their ability to hunt. The typical prey of a bat is the moth – an object not much larger than a couple of centimeters. Bats use ultrasonic echolocation methods to detect the presence of moths in the air. But why ultrasound? The answer lies in the physics of diffraction.

As the wavelength of a wave becomes smaller than the obstacle which it encounters, the wave is no longer able to diffract around the obstacle, instead the wave reflects off the obstacle. Bats use ultrasonic waves with wavelengths smaller than the dimensions of their prey. These sound waves will encounter the prey, and instead of diffracting around the prey, will reflect off the prey and allow the bat to hunt by means of echolocation.

Bats typically produce sound of frequency around 50,000 Hz corresponding to a wave length of 0.68 cm (λ = c / f = 340 m/s / 50,000 Hz). This wavelength is smaller than the dimension of a moth.