MSC offers its clients Adaptive Noise Control solutions which, in certain situations, can be a highly efficient way to decrease low-frequency noise that is very difficult and/or expensive to control using passive means.

What is ANC?

Adaptive control is sound field modification, particularly sound field cancellation, by electro-acoustical means. Adaptive noise control (ANC) is achieved by introducing a canceling “anti-noise” wave through an appropriate array of secondary sources. This produces a sound field that is an exact mirror-image of the offending sound. The speaker and/or actuator thus cancels the sound or vibration signal introduced, while dependent on the situation, can result in dramatically reduced sound levels.

Due to the availability of inexpensive microprocessors, ANC - where an interfaced sound wave or vibration is used to reduce the noise and/or vibration level, most effective on the low end frequency range, can reduce the noise/vibration at its source.

The two forms of ANC that are currently in use are "Airborne ANC" and "Vibration ANC":

• ANC - Vibration Reduction
  ANC vibration system cancels vibration by generating mirror-image signals of the unwanted vibration, feeding them back through the microprocessor to the source 180% out of phase, canceling the vibration at the source. Going to the source of the problem these ANC systems eliminate the need for heavy vibration materials to be used after the fact. On boats and cars this translates into "lighterweight" fuel efficiency at new levels.
  
  An example of this would be an ANC application for an engine mounting system that would eliminate the resulting engine vibration from entering the frame and in turn other components.
  
  
• ANC - Airborne Reduction
  This method use's speakers, microphones and controllers in a controlled "spatial air-field" noise manipulation.
  
  These airborne systems are current most effective in ventilation systems, mostly in office buildings. The ANC airborne system work in this manner. The system consisting of two microphones, a loud speaker and a microprocessor controller. The controller analyzes noise picked up by the microphones, processing a 180-degree out-of-phase antinomies that is played through loudspeakers to cancel the offending noise.
  

Where can ANC be utilized?

Weight/space sensitive applications such as boats are ideal instances of where ANC can be a highly recommended alternative to traditional means of controlling low frequency noise situations.

The traditional approach to attenuate acoustic noise uses passive material techniques such as enclosures, barriers and silencers. These passive techniques are suitable and are preferred for high frequency noise applications. However to effectively reduce low frequency noise situations they often need to be relatively large, very heavy, and costly to manufacture.

In applications where weight and space are not an issue, these passive techniques may be acceptable and are relatively easy to design and build. However when weight and space are at a premium, such as in the transportation (cars, boats, airplanes) ANC can be a more effective alternative.

MSC and Adaptive Noise Control

This technology is moving out of the laboratory as companies begin to develop products that curb noise pollution in the environment and the work-place. This technology is still very new and very expensive to develop in one off applications, but there are generic products that can sometimes fit your needs. Trust that MSC will provide you with the best ANC products and solutions for your needs.

MSC has been actively researching this field since 1990 and our engineers have followed this technology from its inception. If ANC is the best solution for your particular situation MSC can provide with the services you need.

Marine Sound Control
Customer Service Department
Liberty Road
P.O. Box 663
Readfield, ME 04355

1-207-685-7393