Centre of mass displacement (left panels) and corresponding power spectra density profiles (right panels) for the three simulations of our 3D loop. The time-distance maps of the displacement along the x-direction show the magnified (×20) signal projected along the z-axis for visualisation purposes. Only the coronal part of the loop is depicted. Shown are the simulations with the driver (top), with the symmetric initial pulse (middle), and with the asymmetric pulse (bottom).