A multi-fan apparatus and method incorporates mutual active cancellation
of fan noise and/or vibrations. The multi-fan apparatus includes two or
more fans circuits, each comprising a fan, a fan speed controller and a
separate tachometer, and a fan phase controller. The phase controller is
connected to at least one fan speed controller and to each tachometer.
Each fan's speed is independently and dynamically maintained at the same
set speed by the fan speed controllers using an independent control
loops. A noise and/or vibration cancellation phase difference between
fans is determined in order to achieve destructive interference of
pressure waves and, thus, noise and/or vibration reduction, in
pre-determined region of a system incorporating the multi-fan apparatus.
The phase controller establishes and maintains this cancellation phase
difference between the fans based upon feedback from the tachometers.