Signal Processing - November 2016 - 61

SIGNAL PROCESSING
FOR SMART VEHICLE TECHNOLOGIES

Prasanga N. Samarasinghe,
Wen Zhang, and Thushara D. Abhayapala

Recent Advances in Active Noise Control
Inside Automobile Cabins
Toward quieter cars

SKY IMAGE LICENSED BY GRAPHIC STOCK
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M

Digital Object Identifier 10.1109/MSP.2016.2601942
Date of publication: 4 November 2016

1053-5888/16©2016IEEE

inimization of interior cabin noise has been a key topic of research in the automobile industry for the last two decades. This problem was initially approached
via passive noise cancelation methods, where physical treatments such as
structural damping and acoustic absorption were used. However, with vehicle
manufacturers striving for more economical and lightweight designs,
the resulting car interiors invariably became noisier due to the
increased structural vibrations. These noise fields are generally dominanted by low frequencies (i.e., 0- 500 Hz )
[1], [2], hence, the conventional passive noise cancelation approaches are less effective. In an attempt
to resolve the aforementioned problem, active
noise control (ANC) methods were developed
where secondary sources were proposed to
attenuate the noise inside the cabin. With
modern in-car entertainment systems providing four to six built-in loudspeakers,
the addition of an ANC system comes at a
relatively low additional cost.
In practice, in-car ANC is achieved
by producing a secondary signal(s) that
cancels the noise generated by the noise
source(s). The residual difference between
these two components is measured using
a microphone(s) placed inside the cabin and
is minimized using a feedforward/feedback
control system [3]. Feedforward systems use a
time-advanced "reference signal(s)" correlated
with the noise signal to attenuate the primary noise
field, whereas feedback systems tend to attenuate the
overall measured noise. The basic concept behind ANC
inside vehicles is described in Figure 1, which shows how a
secondary sound field cancels out the undesired noise field utilizing an adaptive controller. Since the noise observed inside vehicle cabins is
often random and time varying, the aforementioned control systems are required to be
adaptive. While the theory and concept behind ANC systems are quite straightforward,
their practical implementation and performance are often hindered by factors such as
the noise field complexity inside the car geometry, cost, adaptive system convergence time, system stability, noncausality and poor spatial coverage. Over the
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Table of Contents for the Digital Edition of Signal Processing - November 2016

Signal Processing - November 2016 - Cover1
Signal Processing - November 2016 - Cover2
Signal Processing - November 2016 - 1
Signal Processing - November 2016 - 2
Signal Processing - November 2016 - 3
Signal Processing - November 2016 - 4
Signal Processing - November 2016 - 5
Signal Processing - November 2016 - 6
Signal Processing - November 2016 - 7
Signal Processing - November 2016 - 8
Signal Processing - November 2016 - 9
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Signal Processing - November 2016 - 21
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Signal Processing - November 2016 - Cover3
Signal Processing - November 2016 - Cover4
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