Further Developments of Ultra-Low Noise and Highly Efficient Axial Flow Fan for Industrial ApplicationsDuring the last years there has been a very strong pressure by the market to get cooling systems limiting the noise pollution and the energy consumption. These requirements are today including systems equipped with small size fans (4 to 7), but for this application there is not a product able to satisfy properly both requirements at the same time. When the very low noise is requested in general it is now necessary to give up the high efficiency,