The three P's
There are three key properties that are essential in all active noise cancelling applications.
Without addressing all of these, it is not possible to achieve good
attenuation of all noise frequencies, in all directions. Specifically
for a fan, the solution must be able to suppress noise upstream as
well as downstream.
To reduce noise successfully, the noise reduction component needs to
be able to generate and absorb sound within the entire targeted
Low frequencies are harder to target due to the need of powerful
components. The physics behind RotoSub makes it very powerful in the
demanding low frequency area. This makes the component perfect in
active noise control. A small component with large noise
Without correct phase, noise suppression will not work. Noises emanating from a fan/ventilation system have a very
complicated phase structure.The noise is not only generated by the
fan blades but also by the interaction of the rotating flow with
Anti sound generated from a RotoSub-fan
follows this complicated phase structure. This means that the anti
sound will reduce noise all the way down the flow. It also means that
RotoSub will reduce noise upstream and downstream simultaneously.
To actively reduce noise, the anti-noise source needs to be inserted
in the heart of the flow. When using active noise control, position is
A noise source targeted with active noise control, will have noise
maxima and minima unless the noise and anti-sound can be successfully
joined. The RotoSub uses the fan for anti-sound, positioning the
component in the optimum position, in flow at the noise source.