Performance prediction A sonar target is small relative to the sphere, centred around the emitter, on which it is located. Therefore, the power of the reflected signal is very low, several orders of magnitude less than the original signal. Even if the reflected signal was of the same power, the following example (using hypothetical values) shows the problem: Suppose a sonar system is capable of emitting a 10,000 W/m2 signal at 1 m, and detecting a 0.001 W/m2 signal. At 100 m the signal will be 1 W/m2 (due to the inverse-square law). If the entire signal is reflected from a 10 m2 target, it will be at 0.001 W/m2 when it reaches the emitter, i.e. just detectable. However, the original signal will remain above 0.001 W/m2 until 3000 m. Any 10 m2 target between 100 and 3000 m using a similar or better system would be able to detect the pulse, but would not be detected by the emitter. The detectors must be very sensitive to pick up the echoes. Since the original signal is much more powerful, it can be detected many times further than twice the range of the sonar (as in the example).
Performance prediction A sonar target is small relative to the sphere centred around the emitter on which it is located Therefore the power of the reflected signal is very low several orders of magnitude less than the original signal Even if the reflected signal was of the same power the following example (using hypothetical values) shows the problem Suppose a sonar system is capable of emitting a 10000 W/m2 signal at 1 m and detecting a 0001 W/m2 signal At 100 m the signal will be 1 W/m2 (due to the inverse-square law) If the entire signal is reflected from a 10 m2 target it will be at 0001 W/m2 when it reaches the emitter ie just detectable However the original signal will remain above 0001 W/m2 until 3000 m Any 10 m2 target between 100 and 3000 m using a similar or better system would be able to detect the pulse but would not be detected by the emitter The detectors must be very sensitive to pick up the echoes Since the original signal is much more powerful it can be detected many times further than twice the range of the sonar (as in the example)