Humans can detect (or hear) sound within the 20HZ to 20,000HZ frequency range. The sound waves travel into the ear where a "hammer" hits a "window" according to the sound waves. On the other side of the window is fluid and when the window is struck (by the hammer) it causes waves to form within this fluid. There are projects inside the water similar to hair and when the waves strike them they transmit a signal. This is a oversimplified explanation hopefully its good enough