Acoustic emission (AE) is an effective tool to evaluate the damage progression qualitatively and it can be used to assess important damage mechanism points of a structural element during loading. These assessments are made either by signal-based analyses or parameter-based analyses. In order to investigate the behavior of a reinforced concrete element strengthened with carbon fiber reinforced polymers (CFRP), both mechanical and acoustic information have been considered independently in several studies. However, it is important to combine both the mechanical and acoustic energy information to make a more comprehensive damage characterization. In order to perform a deeper analysis of CFRP-strengthened reinforced concrete structure's damage evolution, a unitless function so called "sentry" that combines both the mechanical and acoustic energy information is employed in this study. This function is expressed in the terms of the logarithmic ratio of the strain energy (E-s) and the acoustic energy (E-AC).