Sharks do not have external ears. Instead, a tiny duct carries sound waves to the inner ear. Sharks can also detect sound with their lateral line system. This system is made up of hundreds of pores along a line on the side of the shark's body. It is also highly sensitive to wave movements, pressure changes and vibrations in the water.
Sharks can sense electrical impulses produced by muscle movement in prey animals.
This sense helps them detect animals hidden beneath the sand. Scientists have demonstrated that sharks are able to learn at a rate similar to white rats and pigeons. Skates, rays and ratfishes are close relatives of sharks. Sharks and Rays of the Pacific Coast . Gruber Samuel H. Ed. 1991.