Abstract
Active noise control is a technique to cancel unwanted
sound using adjustable secondary sound. In active sound
profiling, the target is to obtain a certain sound field
or profile and the power over specific frequencies can be
altered in a desired way, even by amplifying it. Active
sound profiling can be used for increasing the sound
quality in a passenger car, for example, by modifying the
engine noise inside the car cabin.
A fundamental algorithm in active sound profiling is the
commandFXLMS (CFXLMS) algorithm, which is an extension
of the famous FXLMS algorithm widely used in active noise
control. The computational demand of the CFXLMS
algorithm becomes excessive in multiplechannel systems
with engine noise components to be controlled using
several loudspeakers and microphones. The most
timeconsuming part of the CFXLMS algorithm is the
filtering of the reference signals. In order to reduce
the computational burden, a new way to modify the
reference signals in narrowband systems has been
developed in this work. Instead of conventional filtering
operations, the new method is based on delaying the
sinusoidal reference signals and modifying their
amplitude.
The algorithm should work reliably and maintain stability
in all operating points. In this work, an adaptive
leakage has been developed for the CFXLMS algorithm to
increase its robustness. The objective is to limit the
adaptive filter coefficients at frequencies where the
phase shift of the plant is large. Such phase shifts
occur at resonances, for example, and the performance of
the algorithm is drastically degraded. In this work, the
CFXLMS algorithm has also been combined with the
EEFXLMS algorithm so that frequencyindependent step
sizes can be used. This increases robustness and enables
faster tuning of the algorithm.
The developed algorithm has been tested in a simulation
model and in an experimental active sound profiling
system installed in a car. The results prove that the
algorithm works with sufficient accuracy. The convergence
is fast and stability is maintained in all operating
points.
Original language  English 

Qualification  Licentiate Degree 
Awarding Institution 

Place of Publication  Espoo 
Publisher  
Print ISBNs  9789513874575 
Electronic ISBNs  9789513874582 
Publication status  Published  2012 
MoE publication type  G3 Licentiate thesis 
Keywords
 active noise control
 active sound profiling
 commandFXLMS algorithm
 sinusoidal signal filtering
 adaptive leakage factor
Fingerprint Dive into the research topics of 'Development of a robust and computationallyefficient active sound profiling algorithm in a passenger car: Licentiate thesis'. Together they form a unique fingerprint.
Cite this
Kataja, J. (2012). Development of a robust and computationallyefficient active sound profiling algorithm in a passenger car: Licentiate thesis. VTT Technical Research Centre of Finland. http://www.vtt.fi/inf/pdf/science/2012/S5.pdf