When a vehicle is set in motion, its flow noise level increases with the speed. If the surface is rough, flow noise level increases with speed and without any noticeable time lag. If the surface is highly polished, it takes a few seconds for the flow noise to build up. As a consequence, the level of the flow noise and its spectrum are dependent upon the history of the flow before the flow reaches the sound receiver. The amplitude distribution of the flow noise turns out to be very nearly Gaussian. However, in certain instances flow noise is emitted in bursts. Experimental results will be presented.