Material that sends sound from water to air could help eavesdroppers

A material that can transport underwater sounds into the air, allowing them to be heard clearly above the water’s surface, could be used for monitoring aquatic environments or eavesdropping on underwater communications.

Sound normally can’t travel between water and air because of a mismatch in densities between the two mediums. It instead reflects at the boundary.

Now, Bin Liang at Nanjing University in China and his colleagues have developed a material that allows almost all of the sound to pass …