​Graphene audio system mimics bat communication

A team of physicists at the University of California, Berkeley, has developed a graphene-based microphone and speaker system that can mimic the ultrasonic communication used by bats and dolphins.

The devices could be used to transmit signals underwater, but with far more fidelity than current sonar or ultrasound devices, according to the team. It is also claimed that the system could be used to communicate through solid objects such as steel, which electromagnetic waves are unable to penetrate.

The system mimics the ultrasonic communication used by bats and dolphins.
The system mimics the ultrasonic communication used by bats and dolphins.

“Sea mammals and bats use high-frequency sound for echolocation and communication, but humans just haven’t fully exploited that before, in my opinion, because the technology has not been there,” said UC Berkeley physicist Alex Zettl, one of the lead researchers on the project.

“Until now, we have not had good wideband ultrasound transmitters or receivers. These new devices are a technology opportunity.”

The research, published this week in the Proceedings of the National Academy of Sciences, began two years ago with Berkeley postdoctoral fellow Qin Zhou building a set of speakers using a sheet of graphene for the diaphragm.

Graphene membranes are just one atom thick and are significantly more efficient than the paper or plastic used in conventional speakers. The graphene speakers convert over 99 per cent of inputted energy into sound, compared to eight 8 per cent in off-the-shelf sound equipment. 

“Because our membrane is so light, it has an extremely wide frequency response and is able to generate sharp pulses and measure distance much more accurately than traditional methods,” said Zhou.

The team tested the ultrasonic microphone in a local park where they knew there were bats
The team tested the ultrasonic microphone in a local park where they knew there were bats

After building the speaker, the team worked on developing the electronic circuitry to build a microphone with a similar graphene diaphragm. Once complete, they tested the ultrasonic microphone in a local park where they knew there were bats. With the recordings slowed down to 10 per cent of normal speed, the high frequency communication of the bats was clearly audible.

According to Zettl, the technology would have been extremely difficult to develop just a few years ago, but has been made possible by advances in graphene production.

“Over the past decade the graphene community has come together to develop techniques to grow, transport and mount graphene, so building a device like this is now very straightforward; the design is simple,” he said in a statement.