In this case the observer is using the detector in Heterodyne mode. The ultra sonic call is converted so the sound can be heard by humans.

---

An observer has chosen a suitable place for bats during the evening, this detector converts the ultrasonic bat calls so they are within the hearing range of humans and with practice the species can be identified.

---

Size: 4000px × 6016px
Location: Caergeiliog, United Kingdom
Photo credit: © Jim Clark / Alamy / Afripics
License: Licensed
Model Released: Yes

Keywords: anglesey, bat, citizen, detector, earphones, evening, headphones, heterodyne, mon, naturalist, nature, observer, pensioner, science, senior, study, summer, survey, uk, wales, wildlife, woodland, ynys