Sensor detects underwater sound direction

A new sensor that measures the motion created by sound waves under water could allow the U.S. Navy to develop compact arrays to detect the presence of enemy submarines. These new arrays would detect quiet underwater targets, while also providing unambiguous directional information. Using optical fibers, researchers at the Georgia Institute of Technology have found a way to create a sensor that detects the direction from which a sound is coming under water. This directional component is an important improvement over the current technology, researchers said.Inside a fish's ear, there are thousands of tiny hairs that move when a sound wave passes through the fish. These hairs then communicate with nerves allowing fish to hear under water. Because fish excel at detecting sound so they don't get eaten, the Georgia Tech researchers chose the fish hearing system as their model, they said.Research scientists from the School of Mechanical Engineering, have developed a more compact, more sensitive sound detector that can provide unambiguous directional information. In addition, the sensor can be modified to measure the water deformation, known as shear, associated with a sound wave, a quantity typically difficult to measure because it requires very sensitive instruments. This new sensor shows promise that it can be successfully modified to detect this acoustic shear, which will enhance the directional information, the researchers said. The sensor is designed with two small plates attached by a hinge. One plate is held rigidly, and the other plate, made of a composite material with the same density as water, is free to move. The freely moving plate shifts in the sound field and follows the motion of water. A light signal sent through an optical fiber glued to both plates is modified by the motion of the freely moving plate. Analyzing the light signal with a photodetector provides information relative to the sound waves.

Source: physorg.comAdded: 21 February 2007