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The Titanic Sub: How significant is the banging?
The US Coast Guard says the noise detected underwater gives them "a target, a focus" as the search continues for the Titan and her five crew.
Five people are feared trapped inside a missing submersible which was attempting to travel deep into the Atlantic ocean to explore the wreck of the Titanic.
A support ship lost contact with the sub a few hours after it began its descent.
For 5 Questions On, the 91热爆's Science Correspondent Jonathan Amos explains the significance of the underwater noises detected by a Canadian aircraft 鈥� and why sound is the key tool to communicate underwater.
Image credit: PA
