If you want to make the best equipment to listen to underwater sounds, where should you look? Most people would point you to the sales department of a high-end audio company, but a group of Stanford researchers are looking to Orca whales for their inspiration.
Orca whales have ears that can sense a wide range of frequencies in an environment with wildly fluctuating water pressures. This is much different from a human ear which can only hear limited frequencies under relatively constant air pressure. The current crop of underwater microphones are more like human ears. They record a limited amount of sound and don't perform well under pressure.
The team from Stanford hopes to change all that with their Orca-inspired hydrophone. Their microphone has a thin membrane that is 25x thinner than plastic wrap. Small nano-sized holes let water flow freely through the membrane in response to water pressure changes. Lasers and mirrors are used to detect even the slightest change in the membrane and a fibre optic cable carries the data back to the researchers.
This is done on a very small scale with three tiny diaphragms housed in a shell not much bigger than a pea. The trio function as one sensor and can pick up noises as loud as a TNT explosion or as quiet as a whisper. It can also hear sound frequencies across 17 octaves. Its sensitivity and size could revolutionize underwater research for marine biology and even particle physics. [Science Blog via The Scuttlefish]
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