The applications of NDT are varied and recently, an NDT technique known as ‘modal analysis’ was adopted in railway engineering in order to measure track behaviours under either train services or man-made loadings. OVER THE PAST decade, modal testing has become an effective means for identifying, understanding, and simulating dynamic behaviour and responses of structures. One of the techniques widely used in modal analysis is based on an instrumented hammer impact excitation. By using signal analysis, the vibration response of the structures to the impact excitation is measured and transformed into frequency response functions (FRFs) using the Fast Fourier Transformation (FFT) technique. Subsequently, the series of FRFs are used to extract modal parameters such as frequency, damping, and corresponding mode shape. In a range of practical applications the modal parameters are required to avoid resonance in structures affected by external periodic dynamic loads. Practical applications of modal analysis span over various fields of science, engineering and technology.