Type of Document Master's Thesis Author Tu, Yifeng Author's Email Address email@example.com URN etd-52597-0349 Title Multiple Reference Active Noise Control Degree Master of Science Department Mechanical Engineering Advisory Committee
Advisor Name Title Burdisso, Ricardo A. Saunders, William R. Fuller, Christopher R. Committee Chair Keywords
- eigenvalue spread
- decorrelation filter
- active noise cancellation
- adaptive filter
Date of Defense 1997-03-25 Availability unrestricted AbstractThe major application of active noise control (ANC) has been
focused on using a single reference signal; the work on
multiple reference ANC is very scarce. Here, the behavior
of multiple reference ANC is analyzed in both the frequency
and time domain, and the coherence functions are provided to
evaluate the effectiveness of multiple reference ANC.
When there are multiple noise sources, multiple reference
sensors are needed to generate complete reference signals.
A simplified method combines those signals from multiple
reference sensors into a single reference signal. Although
this method could result in satisfactory noise control
effects under special circumstances, the performance is
generally compromised. A widely adopted method feeds each
reference signal into a different control filter. This
approach suffers from the problem of ill-conditioning when
the reference signals are correlated. The problem of
ill-conditioning results in slow convergence rate and high
sensitivity to measurement error especially when the FXLMS
algorithm is applied. To handle this particular problem,
the decorrelated Filtered-X LMS (DFXLMS) algorithm is
developed and studied in this thesis.
Both simulations and experiments have been conducted to
verify the DFXLMS algorithm and other issues associated
with multiple reference ANC. The results presented herein
are consistent with the theoretical analysis, and favorably
indicate that the DFXLMS algorithm is effective in improving
the convergence speed.
To take the maximum advantage of the TMS320C30 DSP board
used to implement the controller, several DSP programming
issues are discussed, and assembly routines are given in
the appendix. Furthermore, a graphical user interface (GUI)
running under Windows' environment is introduced. The main
purpose of the GUI is to facilitate parameters modification,
real time data monitoring and DSP process control.
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