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Active noise control - pneumatic transport system

The problem

The anti-noise system

Centrifugal fans are often used to convey material around production lines. In one drinks canning plant, a six-bladed radial fan in the filler room, delivering 3 m3/s of air, supplied air to move cans along lines. The fan produced a tone at about 300 Hz with an A-weighted noise level of over 90 dB.

The solution

It was decided to adopt an active noise control solution. This consisted of a digital signal processing controller producing a digital model of the noise. A signal microphone fed information to the controller which then produced an inverse sound wave from the loudspeaker. This 180 out-of-phase wave combined with the noise, cancelling it by destructive interference. A second microphone analysed the operation of the system and adapted it continuously to take account of system changes.

The cost

£6500. (1995)

The result

A reduction in the tonal noise by 22 dB. There was no interference with the work process, such as might occur with an enclosure

Source

Equipment manufactured by Digisonix Inc, USA.

Updated 2010-04-02