Numerical simulation of ultrasonic wave propagation using methods such as finite element or finite difference is computationally expensive particularly when (a) structural dimensions are high, (b) inspection at higher frequencies (due to short wavelengths), and (c) in complex materials that are not isotropic. This paper discusses a numerical technique, which is similar to FEM, but works in frequency domain and has advantage of more accurate results in quick computational time called the spectral element method (SEM). When the second order partial differential wave equation transformed to frequency domain by Continuous Fourier Transform, the wave equation transforms to ordinary differential equation (ODE) that has exact solution. This paper discusses simulation of Lamb wave modes and Time of Flight Diffraction Technique in isotropic plates. © 2006 American Institute of Physics.