Fan noise control

It believes the solution is aerodynamic noise control technology as installed by Red Bull Technology. 

Here, aerodynamic inserts were designed, manufactured and installed inside the fan casing within a few hours. The 218Hz low frequency tone was reduced by a factor of around 1000 (a record for this technique), eliminating the problem at source for the fan's lifetime, without maintenance and without affecting fan efficiency.

Terry Brice of Red Bull Technology said: "The INVC technique not only produced a fantastic result, but it’s also very satisfying as an elegant engineering solution”.