A new damage detection technique is presented which can localize a breathing crack in a metallic rod-like structure. Biologically inspired by the combination tone phenomenon which occurs in the human auditory system, the nonlinear signal produced at the difference combination frequency of the two harmonic excitation frequencies ( f1 - f2 ) is used to detect and localize the breathing crack. An experimental investigation is performed to verify the proposed approach. Compared to previously introduced techniques for detection of breathing cracks based on super-harmonic or subharmonic nonlinear response signals, the proposed approach is much more robust and easier to implement.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.