Studying bat echoes through computer reconstruction

Bats detect surrounding objects using echolocation, calculating distances and shapes based on echoes received from their emitted sound pulses. Because the bats are moving, the Doppler effect causes the frequencies of the echoes to shift, sometimes out of the band of high auditory sensitivity of bats. Bats will actively adjust for this by shifting the pitch of their pulse so the echo from its target will be audible, in a process known as Doppler shift compensation behavior.

Studying this behavior, however, is challenging from a technical perspective. Ground-based microphones are unable to reproduce the Doppler-affected sounds, and microphones small enough to be mounted to the bat itself lack the dynamic range to pick up both the initial pulse and the much quieter echoes.

To solve this problem, Teshima et al. combined a bat-mounted microphone with a computer reconstruction of the produced echoes. Their hybrid technique allowed them to study how a bat changes object focus during flight.

“We analyzed the echoes from each object, and it is clear that a bat flying in a circle among four walls always focuses its attention on one wall and smoothly shifts its attention to the next wall,” said author Yu Teshima.

The researchers believe their technique will enable a new line of research studying bat echolocation from the bat’s perspective. They are also excited about the possibility of developing practical technologies built around bat behaviors.

“If we can model bats’ sensing strategies, we will be able to apply them to engineering applications,” said Teshima. “We would like to bring the ‘bat brain’ into the field of sensing technology-based engineering and create a new technology of biological origin.”

Source: “Reconstruction of echoes reaching bats in flight from arbitrary targets by acoustic simulation,” by Yu Teshima, Yuta Hasegawa, Takao Tsuchiya, Ryota Moriyama, Shoko Genda, Taku Kawamura, and Shizuko Hiryu, The Journal of the Acoustical Society of America (2022). The article can be accessed at https://doi.org/10.1121/10.0009916 .