Signal Processing - November 2016 - 70
Spatial sound field control involves acoustic control over
of seated passengers, the opening and closing of windows/
a continuous spatial region utilizing a finite set of transdoors, and vehicle interior production tolerances. To ensure
ducers distributed over the region of interest. Two wellconsistent ANC performance, it is important to improve sysdeveloped techniques to achieve spatial sound field control
tem robustness while minimizing uncertainties. The typiare wavefield synthesis [45] and higher-order ambisonics
cal approach to achieve this is via measuring and modeling
(HOA) [46]. Currently, HOA is the only technique utilized
different components of overall uncertainty as accurately as
for spatial noise cancelation inside automobiles, and, therepossible under realistic conditions, and setting the ANC sysfore, the overview given in this section will be limited to
tem parameters to guarantee robustness.
HOA. HOA is conceptually based on the cylindrical/spheriIn addition to the aforementioned concerns, another key
cal harmonics-based solution to the wave equation. This
aspect that affects the implementation of ANC in production
solution represents the incident pressure at any arbitrary
vehicles is the integration of the ANC system to the existing
point x within a control region of radius R , with respect to
audio system for parallel usage. Initially, ANC solutions were
added as an extra control unit (DSP audio amplifier) causits origin by [47]
ing no impact on the existing audio system, however it was
p (x, k) =
soon deemed to be ineffective with regard to cost, weight, and
Z N
space. A subsequent ANC solution was to add some dedicated
] / a n (k) J n (kr) e inz
2-D region with x = (r, z)
] n =-N
processing resources for ANC into the existing audio system
[
,
N
n
(i.e., plug-in module for head unit with dedicated DSP), which
] / / a nm (k) j n (kr) Ynm (i, z) 3-D region with x = (r, i, z)
]
omits the need for an additional control unit while minimizing
\ n = 0 m =-n
added weight and space. A more recent and improved ANC
(5)
solution is to fully integrate ANC in the form of software into
the existing audio system. This is done by 1) adding ANC as
where k = 2rf/c represents the wave number with f and c
a software on the amplifier without extra processing unit (e.g.,
representing frequency and speed of sound respectively, a
Analog devices' SHARC processor) or 2) integrating funcdenotes the HOA harmonic coefficients, J n ($) and j n ($) repretional software using system-on-chip (SOC) solutions (e.g.,
sent the cylindrical and spherical Bessel functions of order n ,
NXP chip for the Bose Active Sound Management System).
respectively, Ynm ($) denotes the spherical harmonic funcWhile the commercial application of the
tion, and N = ^kRh is the summation's
aforementioned solutions are still limittruncation limit (commonly referred to
Another key aspect
ed, they are expected to be utilized more
as sound field order) derived based on
that affects the
broadly in the near future. One more issue
inherent properties of Bessel functions.
implementation of ANC
that affects ANC implementation in massThe main advantage of the aforemenin production vehicles
produced vehicles is system tuning during
tioned decomposition is that it gives the
production. This involves the measurement
ability to record or produce an entire
is the integration of the
of secondary path transfer functions and
continuous spatial sound field by conANC system to the
the determination of algorithm parameters
sidering only a finite set of coefficients.
existing audio system
such as the number of engine orders to canWhen recording a spatial sound field,
for parallel usage.
cel. With the uncertainty issues mentioned
these coefficients have a direct relationabove, and multiple available powertrains,
ship with the microphone outputs in the
it is important to tune the ANC system for each of the vehicle
form P = Ta , where a is a vector of recorded sound field
variants. This task requires a lot of time and manpower and,
coefficients, T is a transformation matrix, and P is a vecwith increasing demand to shorten the vehicle development
tor of microphone recordings. Similarly, when producing a
period, there is an urgent need to opt for advanced CAE techsound field, the above coefficients have a direct relationship
nologies that enable faster tuning.
with the loudspeaker driving signals in the form a = T1 W,
where a is now a vector of desired sound field coefficients,
T1 is a transformation matrix, and W is a vector of loudSpatial sound field control in ANC
speaker
driving signals. Generally, when recording/proUp to this point, we have only discussed ANC techniques that
ducing an Nth-order sound field, there exists a minimum
model the noise field in terms of acoustic modes and structuralacoustic coupling. By now, it is common knowledge that the
requirement of (2N + 1) or (N + 1) 2 sensors/loudspeakers
aforementioned ANC is effective at low frequencies, but have
for two-dimensional (2-D) and three-dimensional (3-D)
limitations at high frequencies due to increased requirement of
sound fields, respectively. This is to avoid the undesired
microphones/speakers and related cost. Recently, research has
effects of spatial aliasing.
been carried out to model noise fields in an alternative domain
When HOA-based spatial sound field control is occupied
such that characteristics like sparsity can be exploited to bring
in ANC, the residual field, the noise field, and the secondary
down the minimum requirement of microphones/speakers.
sound field are first decomposed in to cylindrical/spherical
This concept is based on spatial sound field control, and initial
harmonic coefficients. For example, in 3-D ANC, the freresearch on this topic is described next.
quency transform of (6) is decomposed into
70
IEEE Signal Processing Magazine
|
November 2016
|
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
Signal Processing - November 2016 - 10
Signal Processing - November 2016 - 11
Signal Processing - November 2016 - 12
Signal Processing - November 2016 - 13
Signal Processing - November 2016 - 14
Signal Processing - November 2016 - 15
Signal Processing - November 2016 - 16
Signal Processing - November 2016 - 17
Signal Processing - November 2016 - 18
Signal Processing - November 2016 - 19
Signal Processing - November 2016 - 20
Signal Processing - November 2016 - 21
Signal Processing - November 2016 - 22
Signal Processing - November 2016 - 23
Signal Processing - November 2016 - 24
Signal Processing - November 2016 - 25
Signal Processing - November 2016 - 26
Signal Processing - November 2016 - 27
Signal Processing - November 2016 - 28
Signal Processing - November 2016 - 29
Signal Processing - November 2016 - 30
Signal Processing - November 2016 - 31
Signal Processing - November 2016 - 32
Signal Processing - November 2016 - 33
Signal Processing - November 2016 - 34
Signal Processing - November 2016 - 35
Signal Processing - November 2016 - 36
Signal Processing - November 2016 - 37
Signal Processing - November 2016 - 38
Signal Processing - November 2016 - 39
Signal Processing - November 2016 - 40
Signal Processing - November 2016 - 41
Signal Processing - November 2016 - 42
Signal Processing - November 2016 - 43
Signal Processing - November 2016 - 44
Signal Processing - November 2016 - 45
Signal Processing - November 2016 - 46
Signal Processing - November 2016 - 47
Signal Processing - November 2016 - 48
Signal Processing - November 2016 - 49
Signal Processing - November 2016 - 50
Signal Processing - November 2016 - 51
Signal Processing - November 2016 - 52
Signal Processing - November 2016 - 53
Signal Processing - November 2016 - 54
Signal Processing - November 2016 - 55
Signal Processing - November 2016 - 56
Signal Processing - November 2016 - 57
Signal Processing - November 2016 - 58
Signal Processing - November 2016 - 59
Signal Processing - November 2016 - 60
Signal Processing - November 2016 - 61
Signal Processing - November 2016 - 62
Signal Processing - November 2016 - 63
Signal Processing - November 2016 - 64
Signal Processing - November 2016 - 65
Signal Processing - November 2016 - 66
Signal Processing - November 2016 - 67
Signal Processing - November 2016 - 68
Signal Processing - November 2016 - 69
Signal Processing - November 2016 - 70
Signal Processing - November 2016 - 71
Signal Processing - November 2016 - 72
Signal Processing - November 2016 - 73
Signal Processing - November 2016 - 74
Signal Processing - November 2016 - 75
Signal Processing - November 2016 - 76
Signal Processing - November 2016 - 77
Signal Processing - November 2016 - 78
Signal Processing - November 2016 - 79
Signal Processing - November 2016 - 80
Signal Processing - November 2016 - 81
Signal Processing - November 2016 - 82
Signal Processing - November 2016 - 83
Signal Processing - November 2016 - 84
Signal Processing - November 2016 - 85
Signal Processing - November 2016 - 86
Signal Processing - November 2016 - 87
Signal Processing - November 2016 - 88
Signal Processing - November 2016 - 89
Signal Processing - November 2016 - 90
Signal Processing - November 2016 - 91
Signal Processing - November 2016 - 92
Signal Processing - November 2016 - 93
Signal Processing - November 2016 - 94
Signal Processing - November 2016 - 95
Signal Processing - November 2016 - 96
Signal Processing - November 2016 - 97
Signal Processing - November 2016 - 98
Signal Processing - November 2016 - 99
Signal Processing - November 2016 - 100
Signal Processing - November 2016 - 101
Signal Processing - November 2016 - 102
Signal Processing - November 2016 - 103
Signal Processing - November 2016 - 104
Signal Processing - November 2016 - 105
Signal Processing - November 2016 - 106
Signal Processing - November 2016 - 107
Signal Processing - November 2016 - 108
Signal Processing - November 2016 - 109
Signal Processing - November 2016 - 110
Signal Processing - November 2016 - 111
Signal Processing - November 2016 - 112
Signal Processing - November 2016 - 113
Signal Processing - November 2016 - 114
Signal Processing - November 2016 - 115
Signal Processing - November 2016 - 116
Signal Processing - November 2016 - 117
Signal Processing - November 2016 - 118
Signal Processing - November 2016 - 119
Signal Processing - November 2016 - 120
Signal Processing - November 2016 - 121
Signal Processing - November 2016 - 122
Signal Processing - November 2016 - 123
Signal Processing - November 2016 - 124
Signal Processing - November 2016 - 125
Signal Processing - November 2016 - 126
Signal Processing - November 2016 - 127
Signal Processing - November 2016 - 128
Signal Processing - November 2016 - 129
Signal Processing - November 2016 - 130
Signal Processing - November 2016 - 131
Signal Processing - November 2016 - 132
Signal Processing - November 2016 - 133
Signal Processing - November 2016 - 134
Signal Processing - November 2016 - 135
Signal Processing - November 2016 - 136
Signal Processing - November 2016 - 137
Signal Processing - November 2016 - 138
Signal Processing - November 2016 - 139
Signal Processing - November 2016 - 140
Signal Processing - November 2016 - 141
Signal Processing - November 2016 - 142
Signal Processing - November 2016 - 143
Signal Processing - November 2016 - 144
Signal Processing - November 2016 - 145
Signal Processing - November 2016 - 146
Signal Processing - November 2016 - 147
Signal Processing - November 2016 - 148
Signal Processing - November 2016 - Cover3
Signal Processing - November 2016 - Cover4
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_201809
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_201807
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_201805
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_201803
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_201801
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1117
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0917
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0717
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0517
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0317
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0117
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1116
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0916
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0716
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0516
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0316
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0116
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1115
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0915
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0715
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0515
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0315
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0115
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1114
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0914
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0714
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0514
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0314
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0114
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1113
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0913
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0713
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0513
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0313
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0113
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1112
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0912
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0712
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0512
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0312
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0112
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1111
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0911
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0711
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0511
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0311
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0111
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1110
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0910
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0710
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0510
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0310
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0110
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1109
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0909
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0709
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0509
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0309
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0109
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_1108
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0908
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0708
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0508
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0308
https://www.nxtbook.com/nxtbooks/ieee/signalprocessing_0108
https://www.nxtbookmedia.com