Abstract: Apparatus for inspecting a non axi-symmetric elongate body includes at least one exciter array having a plurality of wave exciters that can be coupled to an exterior surface of the elongate body. A driver unit generates driving signals to excite the wave exciters. Each driving signal for a respective wave exciter in the array is weighted with respect to driving signals to the other wave exciters in the array such that a specific guided acoustic wave mode is excited. A receiving unit includes a plurality of wave receivers for receiving reflected guided acoustic waves. An analysis unit analyzes received waves to assess a condition of the non axi-symmetric elongate body.