Bats Lend an Ear to Sonar Tech


Bats create a three-dimensional acoustic image of insects as they swoop through jungles, fields and forests.

Now, bio-engineers have put together a 3-D computer model of more than 100 bat ears as a first step in designing flying robots that may one day do the same.

The study by researchers in the United States and China in this week’s Bioinspiration & Biomimetics provides insight into how the shape of bats’ ears helps them send and receive pulses of sound that give them information about their environment.

“What we have is a toolkit of components that we can mix together to explain bat ears in nature, and mix those components and make our own bat ears,” said Rolf Mueller, associate professor of mechanical engineering at Virginia Tech and lead author of the new report.

“If somebody says, ‘I need an antenna, and this is what I would like it to do,’ we can mix these components and it would spew out a little shape and this is your bio-inspired antenna.”

Mueller and his colleagues trekked through remote areas of China, Vietnam and Cambodia to capture the bats and take 3D digital images of their ears. What they were really after is the shape of the pinnae, the visible part of the ear outside the head.

The images were analyzed using the same kind of computer program that analyzes human faces and fingerprints.

Mueller says the kind of delicate, ultra-precise sonar used by bats could also be used by farmers to determine whether their wheat fields are infested with destructive pests. Or perhaps to help navigate tiny unmanned drones into crowded neighborhoods looking for trouble.

Both of these applications would require much greater sensitivity of radar and sonar than current technology can muster.

The new 3D bat ear catalog has provided examples of the best shapes to be used for new kinds of antennae.

“If you wanted to build a self-controlled flying vehicle for operating in a forest at night, you would have to build things on it that look like ears,” said James Simmons, professor of neuroscience at Brown University. Mueller’s study “builds a family of artificial bat ears.”

Mueller agreed that his study is the first step toward such a design.

Even if researchers could build such an antenna, and figure out how to detect objects, there is still the problem of processing the signals in the robot’s “brain.”

“The auditory parts of the brain are organized to take advantage of the ear,” Simmons said. “That’s not going to be too easy for engineers to do without serious help from biologists. Digital methods will be fine, just not the ones we use now.”

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