The effect of grazing bias flow interaction on the orifice acoustic impedance has been experimentally investigated.It is shown that the acoustic resistance of an orifice increases slowly with the increase of bias flow speed because of grazing flow effect

but the acoustic resistance is dominated by the bias flow effect when bias flow speed is comparatively high.In addition

there is some difference between grazing inflow and grazing outflow interactions.Finally

an attempt is made to correlate the experimental data in terms of the effective discharge coefficient.