Fan noise - Basic notions and types of fans

Fans are used in a very wide range of sectors: ventilation, air conditioning and air distribution in building and transport, industrial processes, cooling of electric or thermal motors and electronic circuits, household appliances...

Increasing demands for comfort and increasingly stringent regulations are forcing manufacturers to reduce the noise levels of their machines and installations, in which the fan is often one of the noisiest components. The setting of maximum noise levels is now an almost systematic clause in the specifications submitted to fan manufacturers. What's more, the design of low-noise fans is an objective for many manufacturers, as it is an important commercial argument for standing out from the competition.

Fan noise arises primarily from unsteady aerodynamic phenomena associated with the interaction of blades and fixed parts with the flow.

To reduce the noise of a device or circuit into which a fan is inserted, it's not enough to reduce the noise of the fan alone, you must also take care to minimize the installation effect, which most often results in an increase in noise level.

First of all, we need to know and define the geometric characteristics of the different types of fan. This is the subject of this first article. Then [BM 4 178] , we'll look at how to model the mechanisms behind aerodynamic noise and the methods for reducing it, and how to predict and reduce the installation effect.