A system for nondestructively evaluating a sample. An ultrasonic array is used for directing and receiving guided waves to the sample. A matrix switch is used to sequence through the array of transducers and reconstruct the modal waveform by introducing the appropriate time delay for the desired mode. The sequencing sweeps through the dispersion space of all possible guided wave modes for a given plate. The sequencing is used to determine the parameters (frequency and time delay) that will excite the optimal guided wave mode for inspecting a given structure.
 The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.