FM signal advantages Animal echolocation

echolocation call produced pipistrellus pipistrellus, fm bat. ultrasonic call has been heterodyned - multiplied constant frequency produce frequency subtraction, , audible sound - bat detector. key feature of recording increase in repetition rate of call bat nears target - called terminal buzz .

the major advantage conferred fm signal extremely precise range discrimination, or localization, of target. j.a. simmons demonstrated effect series of elegant experiments showed how bats using fm signals distinguish between 2 separate targets when targets less half millimeter apart. ability due broadband sweep of signal, allows better resolution of time delay between call , returning echo, thereby improving cross correlation of two. additionally, if harmonic frequencies added fm signal, localization becomes more precise.

one possible disadvantage of fm signal decreased operational range of call. because energy of call spread out among many frequencies, distance @ fm-bat can detect targets limited. in part because echo returning @ particular frequency can evaluated brief fraction of millisecond, fast downward sweep of call not remain @ 1 frequency long.