The author has outlined three-dimensional characteristics of nappe oscillations for explaining the effect of spoilers. Full-scale models have provided the common tendency of Sound Pressure Levels of the Low Frequency Air Vibration under the increase of the overflow depth of weirs Various combinations of the opening of weir nappes have confirmed the effect of spoilers for restricting the oscillation within narrow limits as well as dicreasing peak Sound Pressure Levels. The author has also proposed the measure to estimate Sound Pressure Levels about the weir width, hight, overflow depth and the distance from the weir.