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Linear Quadratic Gaussian Controllers for
Feedforward Active Noise Control 
Pushing performance and moving towards adaptive control.
 
Annea Barkefors
 Licentiate Thesis, Signals and Systems, 
Uppsala University,  May 2014.
 
The thesis summary 
 in Pdf
    
  Paper copies of the complete thesis can be obtained from
Ylva Johansson,
Signals and Systems Group, Uppsala University, 
Box 534, SE-75121 Uppsala, Sweden.
 
 
 
  
Abstract:
Active noise control is a research area focused on using destructive 
interference of sound fields to attenuate undesired noise. 
Methods for active noise control are best suited for low frequency noise, as the complexity of the problem grows rapidly with frequency. 
Coincidentally, passive means of damping have the opposite quality 
in that they work better for higher frequencies and become bulky and impractical for low frequencies. 
Applications for active noise control range from fan noise in ducts, 
noise-cancelling headphones and noise in cars to propeller induced
aircraft cabin noise.  
 
In this comprehensive summary, the underlying principles of active noise 
control are presented and the control problem is discussed. 
Several aspects of the control system are introduced to give an 
introduction to the research papers that are the basis of this 
licentiate thesis. 
 
The work behind the thesis is focused on a 
Multiple-Input Multiple-Output (MIMO) Minimal Mean Square 
Error (MMSE) Linear Quadratic 
Gaussian (LQG) feedforward controller.  
This controller is shown to achieve uniform damping in an extended 
region in space and push the upper frequency that can be controlled. 
The influence of different design variables has been investigated, 
and the properties of the control path analyzed with consideration 
of its ability to suppress noise of prescribed spectral properties 
over an extended region. In this context, 
it has been shown how to use  the reproducibility of the 
primary noise path by the control path as an 
indication of achievable performance for a given control system. 
 
Finally, the controller has been adapted to follow changes 
in the primary noise statistics, an approach that seems 
promising to considerably raise the performance of the controller.
Publications included in the Thesis:
IEEE ICASSP 2012:
Extending the area silenced by active noise control
using multiple loudspeakers.
 In Pdf    
IEEE ACC 2012:
MIMO design of active noise controllers for car interiors:
Extending the silenced region at higher frequencies.
 In Pdf    
 
ICSV19, 2012:
An investigation of a theoretical tool for predicting
the performance of an active noise control system.
 In Pdf    
 
Paper in IEEE TASLP 2014, Design and analysis of 
Linear Quadratic Gaussian feedforward controllers for 
active noise control.
In Pdf    
 
Paper at InterNoise 2014 on adaptive control in 
nonstationary noise settings.
Related work:
AES 48th Conf. 2012:
Acoustical zone reproduction for car interiors using a MIMO framework.
 
PhD Thesis by Simon Widmark 2018
on causal MMSE filters for personal audio.
 
PhD Thesis by Lars-Johan Brännmak 2011
on robust sound field control for audio reproduction.
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Main
entry in list of publications
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Reseach on audio signal processing 
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