 Their high intensity calls are necessary to even have moderate detection of surroundings because air has a high absorption of ultrasound and because insects’ size only provide a small target for sound reflection.Additionally, the so-called "whispering bats" have adapted low-amplitude echolocation so that their prey, moths, which are able to hear echolocation calls, are less able to detect and avoid an oncoming bat.Calls can be composed of one frequency or multiple frequencies comprising a harmonic series.