ACTIVE NOISE AND VIBRATION CONTROL

How it works

active noise and vibration control block diagram



Active noise/vibration control is the art of fighting noise (or vibration) with opposite phase noise (or vibration). When the opposite phase noise is combined with the original noise, the result is almost silence. The problem to solve to realize such a system is then to calculate that opposite phase noise (or vibration).

An active noise control system uses adaptive digital signal processing to reduce noise at certain places in an enclosure, or in some cases in the whole space of interest (car cabin, airplane fuselage, room, etc). Given a clean reference of the original noise and the sensors measurement at certain error points, the signal processor calculates some control signals to drive the control actuators which produce the opposite phase noise/vibration at the control points. The goal of the calculated control signals is to minimize the sound pressure level (or vibrations) at the control positions as shown in the figure above.







ANVC Applications

Active noise/vibration control is used in many applications including

  • Reduce engine and road noise inside car cabins
  • Reduce engine noise inside airplane fuselage
  • Reduce noise inside residential and office buildings, for instance when those buildings are located near by airports or high ways
  • Reduce machine vibrations which results in longer operation life and less maintenance cost
  • Reduce heavy structures vibrations (railway bridges for instance) which in turn reduces noise and maintenance
  • Many less obvious applications



Audio Examples

The audio examples below show how effective active noise control can be. The sound pressure level measured by the control microphone is recorded before and after switching on the ANVC system. In this case, it took the ANVC system a few seconds to reduce noise at the microphone by 30 dB. The images show the spectrum of the microphone signals before and after applying ANVC.


before

Noise before applying ANVC



after

Noise after applying ANVC



Evaluating ANVC

Two real-time demonstrators are available:
  • The first on OCEAN-ADSP21489 platform. This demonstrator implements an efficient active noise and vibration control system with up to two reference signals, up to 6 error sensors, and up to 8 control actuators.
  • The second on OCEAN-BF592 platform. This demonstrator implements a 32-bit fixed-point active noise and vibration control system with up to two reference signals, up to 2 error sensors, and up to 2 control actuators.

We will be glad to give you more information on active noise and vibration control solutions, please take a moment to contact us.