Numerical instabilities originate from a variety of sources, including mesh nonuniformity, approximate boundary conditions, and nonlinearity. Common practice is to remove the numerical instability by spatially filtering the solution with a high order (compact) filter. The filtering procedure has great impacts on numerical results of the flow field, especially, the sound field. In present paper, two dimensional symmetric jet noise was calculated by means of direct numerical simulation. Different filtering schemes were tested to show their effects on the sound field. In the direct numerical solver, the six order compact finite difference schemes were implemented for spatial derivatives and classical Runge-Kutta scheme for time integrations. The comparisions between tenth order explicit filtering sheme and implict filtering scheme, low storage three step Runge-Kutta scheme and classical Runge-Kutta scheme, staggered grids and collocated grids were explored. The results showed that the filtering schemes between f10 andf20 were the best, which can show obvious plane wave and inhibit the spurious mode. Small time step can remove the spurious fluctuations in time, but it was time consuming to get a convergent solution. The staggered algorithms were the best way to inhibit numerical instability among the filtering strategies.