Editing Sonar (section)

===Target characteristics===
The sound ''reflection'' characteristics of the target of an active sonar, such as a submarine, are known as its [[target strength]].  A complication is that echoes are also obtained from other objects in the sea such as whales, wakes, schools of fish and rocks.

Passive sonar detects the target's ''radiated'' noise characteristics.  The radiated [[Frequency spectrum|spectrum]] comprises a [[continuous spectrum]] of noise with peaks at certain frequencies which can be used for classification.