Boundary layer transition is a fluid mechanics problem with complex flow mechanism. It has been concerned by many researchers in the past century, especially in transition mechanism and flow field evolution. Transition stimulation is commonly regarded as a significant step in most numerical simulations, which is essentially to apply velocity disturbances to the flow field to promote transition. Though these velocity disturbances are extreme small, studies of their effects on the acoustic performance of boundary layer transition are still relatively scarce. Our present work focuses on the effect of velocity disturbances imposed by nonlinear parabolized stability equation (PSE) on the noise of boundary layer transition. To accurately capture flow structures and sound signals, wall-resolved large-eddy simulation (WRLES) coupled with Ffowcs-Williams and Hawkings (FW-H) equation are applied to simulate the flow and acoustic characteristics on a flat plate using the solver OpenFOAM. Linear and nonlinear noise characteristics at laminar, transition and turbulent region are compared in detail. Our results show that 2D T-S wave and subharmonic wave, which are two fundamental modes imposed at the inlet boundary, have slightly affect the dominant frequency and corresponding amplitude of the sound pressure level (SPL) curves.