Frequency and Time domain methods for automatic limiting of responses and notching the input in random vibration are presented. A discrete system of spring and mass is developed based on the transmissibility characteristics obtained from the low-level test. The discrete system is solved in frequency and time domain to estimate the power spectral density (PSD) responses. In frequency domain, PSD responses are determined by extrapolating the frequency response function (FRF) of discrete system for a specified random input. The area under the extrapolated curve is computed analytically and numerically to obtain the equivalent static load. In time domain, a random acceleration versus time signal is generated corresponding to the input PSD specification. The base of the discrete system is then excited by this random input signal and the response of the discrete system is obtained numerically in time domain. The responses in time domain are then converted to PSD to compute the equivalent static load. If the estimated equivalent peak static acceleration is greater than the quasi-static design load, the responses on the test specimen measured during random vibration are limited and input is notched such that the estimated peak acceleration loads are below the quasi-static design load. Two new methods for notching are studied by modelling test specimen response as single/multi DOF system. The first method estimates the limiting PSD by reducing the gRMS of the extrapolated curve in the frequency domain numerically and analytically. The second method estimates the limiting PSD iteratively by Monte Carlo Simulation in time domain for specified random input excitation. The results obtained from these two methods are compared with those obtained from Miles’ Equation.