usually the smaller turbos make more noise. It is the turbo making the noise, not the air box. If you hold a turbine wheel, by the shaft, in your hand, and hit the blades with air from an air hose causing the wheel to spin, it will make the whistle noise in your hand. The faster you spin it, the louder and more high pitched it will get. Can't do it for too long or it burns a hole in your glove from spinning or if your not holding it tight enough, it becomes air born, then GOD help you. Children do not try this at home.