A detection system for identifying deterioration in a structure is provided that has acoustic sensors that receive acoustic emission waves. The acoustic emission wave detected by the acoustic sensor is identified as a hit. An analysis circuit is present that identifies an A state, a B state, and a C state. The B state has increased hit activity from the A state where a rate B is greater than a rate A by a factor of f1. The C state has increased hit activity from the B state where a rate C is greater than the rate A by a factor of f2. An alarm is activated when an amount of time that the C state is identified as being present reaches a value of TM, or alternatively when a threshold value based upon of the number of hits and time in the C state is reached.