Every summer, billions of cicadas emerge from their hiding places, shed their cocoons, and take to their positions in the trees – only to commence making a lot of noise. The reason for making so much noise is to attract the attention of a mate, but this year they may also have attracted the attention of the US Navy who want to study them in order to create a “Cicada Sonar.”
Researchers at the US Naval Undersea Warfare Center are studying the insects to try and create a more effective sonor device. The findings of their recent research were even presented at the International Congress on Acoustics.
The reason the US Navy were first attracted to the idea of a cicada sonar was because of the amount of noise the tiny insects are capable of producing when compared with their body size. Unravelling this secret could mean developing more effective compact sonar devices. Some of these devices do already exist, but they use passive sonar, meaning the sonar listens for other underwater objects, provided they are making more noise than the vessel doing the listening.
Active sonar on the other hand, transmits sound waves into the water and detect objects based on the waves that are bounced back. While more effective, this type of sonar is normally larger and more complicated to install, limiting the types of vessels that can carry it. By better understanding cicadas, it could allow a much smaller device, capable of being fitted to small unmanned vessels.
The US Navy’s cicada sonar would aim to mimic a cicada’s noise production technique – which uses a pair of plates on their thorax, each of which are attached to ribs that bulge outward. Contracting these plates makes the ribs click and a large air sac behind the ribs amplifies this sound. They do this 300 to 400 times a second, and the out-of-sync sounds somehow combine to create a much louder noise.
Have you got anything to share about sonar and cicadas? How effective do you think a US Navy cicada sonar would be?
Image Via: Wikimedia Commons