Most of the ocean is visually inaccessible to humans. Seawater absorbs and scatters visible light, making anything below the sunlit surface appear dark and murky. The ocean is also impenetrable to many communication and geolocation technologies, such as radio waves, GPS, and other forms of electromagnetic radiation.

For scientists wishing to probe the ocean’s opaque interior, sound is one of the most efficient tools available. Sound travels effectively through seawater—a feature known to marine mammals, which have evolved to use sound to communicate, find food, and navigate underwater. Oceanographers have also taken advantage of sound’s ability to propagate through seawater, using underwater acoustic technologies to greatly advance our understanding of the ocean and marine ecosystems. 

But using sound to “see” into a noisy ocean has its challenges, and it can be difficult to distinguish individual acoustic signatures amidst the cacophony of the underwater soundscape. To overcome this challenge, WHOI scientist Ying-Tsong (YT) Lin and a team of engineers are building the first-ever 3D underwater “acoustic telescope.” Analogous to an optical telescope focusing on distant objects in space, this 30-foot diameter, six-armed, star-shaped array of hydrophones will be capable of tuning in to acoustic sources tens to hundreds or even thousands of miles away, isolating them