This paper describes an array sensor of piezoceramic PZT discs with flexible covering layers, which is designed to detect surface elastic waves in structures, such as Rayleigh waves. The sensor is distinguished from conventional “passive” sensors for elastic waves detection because it possesses an ability to actuate an “active” pulse. This indicates that the function of active pulse generation ensures the diagnosis of the structures, where the sensor attached or embedded into, can be accomplished in a smart way including an easy inspection of faults. Actually the sensor has been inspired from human sensory systems in order to apply for smart structure sensing. They utilized 6mm diameter and 0.25mm thick PZT discs for the active array sensor. The performance of the sensor was demonstrated at various experiments of some metal and composite structures that the sensor can be applied for the health monitoring of the advanced smart structure system.