UNDERSTANDING
`ACTIVE NOISE CANCELLA TON
`
`Exhibit 1019
`
`Colin H. Hansen
`
`Samsung v. Jawbone
`IPR2022-00865
`
`Exhibit 1019
`Page 01 of 92
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`

`

`Understanding Active Noise
`Cancellation
`
`
`
`Exhibit 1019
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`Page 02 of 92
`
`Exhibit 1019
`Page 02 of 92
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`

`

`
`
`Understanding Active Noise
`Cancellation
`
`Colin H Hansen
`
`
`
`Taylor & Francis
`Taylor & Francis Group
`LONDON AND NEW YORK
`
`Exhibit 1019
`
`Page 03 of 92
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`Exhibit 1019
`Page 03 of 92
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`

`

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`
`First published 2001 by Taylor & Francis
`2 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN
`Simultaneously published in the USA
`by Taylor & Francis
`nnd Canada
`270 Madison Ave, New York NY 10016
`Taylor & Francis is an imprint ofthe Taylor & Francis Group
`Transferred to Digital Printing 2006
`© 2001 Colin H Hansen
`Thihis book was prepared from camera-ready copy supplied by the author.
`A I
`h
`I
`= No Pp
`ok may be repr nted
`or reproduced or
`Il
`£nts reserved
`art o this b
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`rf
`Ss!
`utilised In any form or by any elect onic, mechanical, or other means, now
`known 0 hereafter Invented, | icluding photocopying ar d recording
`rin
`£, 0)
`Tag
`=
`=
`—
`i
`i
`SC or retrieval system, without permission in writing fromtl
`ing
`ne Library Cataloguing in Publication Data
`alalogue record for this book is available from the British Library
`ae ofCongress Cataloging in Publication Data
`catalog record forthis book has been requested
`SBN 0-41 5-23192-2 (pbk)
`0-415-23191-4 (hbk)
`
`I
`
`d
`
`e
`
`any information sto
`
`*ublisher’s Note
`he publisher has oneto great lengths to ensure the
`Payopr
`ul points out that some imperfecti
`onsin the original maybe apparent
`
`Exhibit 1019
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`Page 04 of 92
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`bli
`1€ publish
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`TABLE OF CONTENTS
`
`PREFACE .... 2... c cece cence nent teen eee eee teen eres ix
`
`ACKNOWLEDGEMENTS........-.. 055-6 s beeen eee ence eee eens x
`
`CHAPTER ONE. A LITTLE HISTORY .........,5- 00-0 e sees ener 1
`1.1 INTRODUCTION .....-.. 00: eee cece renee eee eee ee
`1
`1.2 EARLY HISTORY ...... 00.00 cece eter terete eee tans 2
`1.3 LATER HISTORY .........:2- 0 cece eect eee te teen nneee 5
`1.4 CURRENT COMMERCIAL APPLICATIONS .....-. eee eer eee 5
`1.55 THEFUTURE .......... 000 cece eee eee eee 6
`
`CHAPTER TWO. FOUNDATIONS OF ACTIVE CONTROL........--. 9
`2.1 PHYSICAL MECHANISMS 4.2.6.0: e eee e eee eee eee ees 9
`2.2 BASIC STRUCTURE OF ACTIVE NOISE CONTROL SYSTEMS .
`11
`2.2.1 Adaptive Feedforward Control... 2.0.66 e cece eee eee eens 12
`2.2.2 Feedback Control .......0-. 00-0 eee ee eee nents 16
`2.2.3 Waveform Synthesis .... 2.00. c eee ee eee teens 18
`2.3 CONTROL SYSTEM OPTIMIZATION .......-- 2-50 eee eee ees 19
`2.3.1 Control Source Output Power and Placement ...........-+-: 21
`2.3.2 Influence of Error Sensor Placement ..-.-.---.e eee reece 25
`2.3.3 Influence of Reference Signal Delay and Quality ..........-- 27
`
`CHAPTER THREE. THE ELECTRONIC CONTROLSYSTEM ....... 31
`3.1 INTRODUCTION ...... 0.0 cece eee eee ete neee 31
`3,2. DIGITAL FILTERS (ADAPTIVE CONTROLFILTERS) ........-- 32
`3.3 ADAPTATION ALGORITHMS FOR ADAPTIVE FILTERS...... 36
`3.3.1 Single-Channel FXLMSAlgorithm for FIR Filter
`Weight Adaptation ........ 0.6 c reece eee eee teeter eee 36
`3.3.1.1 Feedforward Control ......... 00 ec eee eee eee 36
`3.3.1.2 Delayed FKLMSAlgorithm ..- 2.0... ++. see eee eee ee 42
`3.3.1.3 Feedback Control ......2. 000-0 e ete ene teens 42
`3.3.1.4 Hybrid Feedforward / Feedback Control ...........--+ 43
`3.3.2 Cancellation Path Transfer Function (or Impulse Response)
`Estimation .. 0.0.0.0. c cect eee terete ete ene teee 44
`3.3.2.1 Random Noise Modelling Signal .........-.-..-.+54: 46
`3.3.2.2 Overall Modelling... 02.00... eee eee ene 47
`3,3.2.3 Comparison of Pseudo-Random Noise and Overall
`AML AANA Anneeann
`AQ
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`
` Understanding Active Noise Cancellation
`vii
`qable of Contents
`3.3.7.1 Killing Select
`:
`ion Instead of Survivor §
`i
`aac Weight String Instead of Binary Erendie Bt BGG Fue 56
`5.5 VIRTUAL SENSING .....- 00s ester eer e reece eee tne e erences 93
`5.5.1 Virtual Sound Pressure (Virtual Microphone) ......-.+--0005 93
`Be qs Mutation Probability and Amplitude 57
`5.5.1.2 Transfer Function Method ....... 00. eee r ese e ences 93
`ene
`ank-Based Selection (Killing and Breedi i) =
`337a Uniform Crossover
`.
`MB). se es. 37
`5.5.1.2 Forward Prediction Method ...........-0--+-sse0055 94
`5.5.2 Virtual Energy Density ....... 00-00 + eee eee eee teen eee 96
`-3./.6 Genetic Algorithm Par. vasa ET SORE A EL BEEF recor 58
`amet
`j
`3.3.7.7 Performance ieemuen er Adjustment ........ 050. 58
`;
`5,6 VIBRATION SENSING OF SOUND RADIATION ........020065 97
`a WAVERORM SYNTHESIS
`isis... 38
`5.7 CONTROL ALGORITHMS FOR VARIOUS SENSING
`STRATEGIES .,....- 00 esc e er ee cere eee teeter esees 106
`IMPORTANT CONTROLLER IMPLEMENTATION 1ccre,
`‘5
`:
`R IMPLEMENTATION
`Issups =
`os2 eaeproceascr Selection |, EMENTATION ISSUES... 60
`5.7.1 Shaped or Distributed Structural Sensors ......-..-+--+++-- 106
`5.7.2 Sound Intensity 2.0.00... cece ee eee eee eee eee eee eee 107
`9.2
`Converter Type and Group
`Delay Cos, Peete eeeeeeee eee aas 60
`3.5.3 Digital Sampling Rate. vey COMSICRIONE cocceasne yes 61
`5.7.3 Energy Density ........-0eeeee eee« Eaeeianea ncaa aie eee 110
`a Algorithm Considerations... 62
`3 :: eccuracy of Controller Output ......0 a
`».6
`Estimation of The Potential of
`ANC VW * rise sigeae 63
`3.5.7 Controller Processor Overload ANCWithout Using a Controller 64
`3.5.8 Numberof Error Siinalsete ah ewes 65
`Eid a
`rnanresntee bee WERE ocweras ora 66
`CHAPTER FOUR. AC-
`4.1 INTRODUCTION...ONTROLSOURCES .......... 69
`4.2 ACOUSTIC SOURCES : , ci RAE SER Hse rncecemte nastiag 69
`4.2.1 Loudspeakers...)t teen eeeeceey 69
`on Tuned Cavity-Backed Panets SERORSOSES ER Peis meena naa gg 69
`2.3 Acoustic Boundary Control ter meewaatins oa oa, 72
`— on Resonator......0000 0 tt tte eee 73
`-2.5
`Compressed AirSources. tee 75
`4.3 VIBRATION SOURCES id NSIS AINE tae ear eamiakebee ..., 75
`a4 lna Pach Actua: ene FFF Slt emcas 75
`-2-4
`Flezo-Electric Stack
`pperepem ie Ge MEN EO eee nar 76
`4.3.3 Inertial dates
`and Magnetostrictive Actuators ...... 0... 77
`4.3.4 Distributed Vibration Acro. ute
`ation Actuato
`ibation UU! #8
`4
`Actuators and Actuator Groualae ene
`Pek: Tuned Vibration Absorbers... teers 78
`-3.6 Other Types of Vibration ia ee 80
`iinee 80
`“HAPTERFIVE. REF
`"
`EREN
`5.1 MICROPHONES ee AND ERROR SENSING ......... 81
`5.2 TACHOMETER REFERENCESIGNALSERS Nan mace are BEEN Sy ea,
`g 81
`-2.1 Waveform Syiithesis
`TTT EEE FRY ee cage 83
`5.2.2 Filtering....,..00 ntti ee eee, 84
`5.2.3 Non-Linear Transformation eo SH Bin conan 84
`2‘2.4 Simple Look-Up Tables .......00 00/1) 85
`-2.5 Time Domain Measurement. . : MeN ET es oni 85
`5.3, SOUND INTENSITY
`Sil MIS ATANG TE Ba Wm eunreer ena atigig E 86
`2 A Pearse ee
`Exhibit 1019
`
`CHAPTERSIX. APPLICATIONS OF ACTIVE NOISE CONTROL ... 111
`6.1 SOME GENERAL CONSIDERATIONS.........00 see see eneee 111
`6.2, APPLICATION EXAMPLES.....-. 0. eects e ener ener terres 112
`6.2.1 Sound Propagation in Ducts .......6-. 00s eee ee eee e eres 112
`6.2.1.1 Plane Wave Propagation .........--+----e+ee eres 112
`6.2.1.2 Higher Order Mode Propagation .......-.-.-.-.+e5 114
`6.2.1.3 Hybrid Active/Passbve Silencers ......--- + eeee eee 114
`6.2.3 Sound Radiation From Vibrating Structures .........-.+--- 114
`6.2.3.1 Physical Control Mechanisms ...........-6-.050-0- 115
`6.2.4 Active Headsets and Ear Muffs .........-.-- 006s reer ees 117
`6.2.4.1 Feedback Systems ......-.-0 002s ee erence eens 118
`6.2.4.2 Feedforward Systems ........--- 2+ seer ener ences 121
`6.2.4.3 Transducer Considerations ....... 600 eee eee ee eee 122
`6.2.5 Sound Transmission Into Enclosed Spaces ........-.--++-- 123
`6.2.5.1 Global Reduction of Low Frequency Tonal Noise
`in Propeller Aircraft... 0.0... 0. cscs ee ee eee eee eee 127
`6.2.5.2 Reduction of Interior Noise in Diesel Engine-Driven,
`Mobile Mining Equipment
`.........-...-2-0-e ees 128
`6.2.5.3 Local Reduction of Broadband Noise in Large Aircraft . 128
`6.2.5.4 Global Reduction of Low Frequency Road Noise in Cars 128
`6.2.5.5 Reduction of Low Frequency Sound Transmission
`Through Double Panel Walls
`.........-.0seeeeeeee 129
`6.2.6 Active Vibration Isolation ......... 6. cee cece eee eee 129
`6.2.6.1 Reduction of Engine Noise Transmitted Into Passenger
`Cars in the Low to Mid-Frequency Range..........-. 129
`6.2.6.2. Reduction of Noise Generated by Naval Ships ........ 130
`6.3 EXAMPLES OF APPLICATIONS WHICH ARE IMPRACTICAL . 130
`6.3.1 Global Reduction of Broadband or High Frequency Tonal
`Noise in Large Aircraft ....... 66. e cece eens 130
`6.3.2 Global Reduction of Broadbandor Transient Noise
`Transmitted into a Building Space ..........-.-.2+-20 005: 130
`
`ACTIVE NO
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`viii
`
`Understanding Active Noise Cancellation
`6.3.4 aaieae of Tonalor Periodic Noise in a Large
`pace Such as a Factory That Contains Man
`i
`y Noise Sources
`,
`,
`6.3.5 GlobalReduction of Broadband Noiseina Large Factory ~ 3
`marr
`6.3.6 Reduction of Broadband Noise Outdoors
`6.3.7 Reduction of Transient Noise Outdoors .
`.
`: . . . ee fe
`REFERENCES ............._..
`
`PREFACE
`
`
`
`eo 133
`APPENDIX A. A LITTLE MATHS ........
`Al INTRODUCTION ................00000000 att i
`A.2 VECTORS ..... 0... cee te i
`A3MATRICES000s me
`A.4 QUADRATIC OPTIMISATION... 150
`APPENDIX B ADDITIONAL INFORMATION
`.....
`B.1 CURRENT RESEARCH .....,...... Nvotes =
`B.2 USEFUL WEB-SITES FOR MORE INFORMATION Pa
`B.2.1 General information e+ + m-. oe. a. en ier
`B.2.2 Commercial Products and Demonstrations : : : : : vee ie
`B,2.3 Research Organisations and Universities . boeveeree 154
`INDEX ..................
`
`
`
`
`
`This book is derived from material used at short courses given by the authoron active
`noise control and was written after several requests were received for a simple text on
`the subjectthat could be understood easily by graduate and undergraduate science and
`engineering students as well as researchers interested in the topic. There are many
`other people who wishto read a brief text on active noise controlso that they:can gain
`enough understanding and knowledge to evaluate potential applications without
`necessarily having to becomean expertpractitioner. It is the intention of the text to
`provide the reader with an overview of the discipline ofactive noise control, with
`detail provided where necessary to enable those interested readers to gain a deeper
`understanding. A basic familiarity with noise control (see, for example, Bies and
`Hansen, 1996) is necessary to be able to understand mostof this book.
`The material in the book is intended as a precursor to more complex books
`available on the subject and may also be expected to provide sufficient background
`for the reader to understand more advanced discussions at conferences and in other
`books. Practical applications are emphasized and control algorithms and structures
`are discussed to the extent necessary to.enable the reader to implement them.
`The book begins with a brief introduction to active noise control followed by a
`sketchy overview of its history from the first patent to the present time. Possible
`future directions are also discussed. In the second chapter, physical mechanisms that
`result in noise reduction are explained in simple terms. This is followed by a
`description of the basic structure of feedforward and feedback control systems (both
`adaptive and non-adaptive) and the process of control system optimisation.
`In chapter3, variousparts of the electronic control system and control algorithms
`are discussed in sufficient detail to allow a full understanding of the principles
`involved and how such controllers may be implementedin practice. Various practical
`implementation issues are also discussed. In chapter 4, suitable active control sound
`source types and their practical implementation are discussed.
`In chapter 5, error
`sensing strategies, error sensors and reference sensors, and practical issues associated
`with their implementation are discussed. In chapter 6, applications of the technology
`are discussed as are a number of commonly mentioned potential applications which
`are impractical. In chapter 7, current and future research directions are discussed and
`information on relevant websites is provided.
`It is hoped that this book will provide the background necessary for the readerto
`understandthe principles underlying active noise control, to apply the principlesto the
`evaluation of potential applications and to use, with a good understanding,
`commercially available hardware and software to implement active noise control for
`the identified applications.
`
`4 SRE GWEN iteresapeiaeie Ha KK Hea PV Ee eee. 155
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`Exhibit 1019
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`Page 06 of 92
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`Exhibit 1019
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`
`A LITTLE HISTORY
`
`
`11 INTRODUCTION
`
`Active noise cancellation, also known as “anti-noise” and “active noise control”
`involves the electro-acoustic generation (usually with loudspeakers) of a soundfield
`to cancel an unwanted existing sound field. The preferred term to describe the
`phenomenon is “active noise control”, because in manycasesit is arguable that
`cancellation is the true mechanism causing the unwanted noise to diminish.
`[s active noise control everlikely to find widespread application in industry and
`consumer goods,oris it forever destined to be a laboratory tool and a rich source of
`research activity for underpaid academics? Hopefully, this question will be one of
`many that will be answeredas the tale in this book unfolds. For now,suffice it to say
`that there are many systemsinstalled in industry to reduce low frequency fan noise
`emanating from air exhaust ducts and quite a few propeller aircraft are already
`benefiting from the technology.
`In addition, mining equipment and truck
`manufacturersare in the process of applying the technologyto their vehicles to reduce
`noise in the driver’s cabin and radiated exhaust noise.
`A typical single-channelactive noise cancellation system consists of:
`* amicrophone reference sensor to sample the disturbance to be cancelled,
`an electronic control system to process the reference signal and generate the control
`signal,
`aloudspeakerdriven by the control signalto generate the cancelling disturbance and
`* anerror microphoneto provide the controller with information sothatit can adjust
`itself to minimise the resulting soundfield.
`The active noise cancellation system just described is known as an “adaptive”
`system as it can adaptitself to changing characteristics of the noise to be cancelled and
`changing environmental conditionsthataffect the acoustic field. Non-adaptive systems
`are not very useful in practice (except in active noise cancelling headsets and ear
`muffs) and are only discussed briefly in this book.
`In the discussionsthat follow, single-channel systems (one loudspeaker control
`source and one microphone error sensor) are used as a basis for describing the
`underlying principles. However, many active noise cancellation systems that are
`implemented in practice are multi-channel systems, consisting of a number of
`microphones and loudspeakers to generate the required cancelling sound field.
`Extension ofthe single-channelsystem to a multi-channel system is relatively complex
`because of the interaction between all of the microphones and loudspeakers. Means
`for implementing multi-channel systemsandthe associated electronic control system
`will be discussed briefly here for completeness.
`Whohas benefited most from all the effort and hundreds of millions of dollars
`
`CHAPTER ONE
`
`
`
`
`
`
`
`
`
`
`
`
`ACKNOWLEDGEMENTS
`
`I would like to express my deep gratitude to mY many graduate students
`colleagues who provided much of the background material on which this hookdd
`based.
`In particular, I would like to thank Dr Ben Cazzolato, Dr Carl Howard Dr
`Colin Kestell, Dr Xun Li, Dr Xiaojun Qiu and Dr Scott Snyder I would also like to
`thank my family for their continuing tolerance throu hout th e preparatio
`
`This book is dedicated to Susan, to Kristy, to Laura and to my parents, Betty
`and Ludwig, without whose support this book would not have been possible
`
`Exhibit 1019
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`Page 07 of 92
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`Exhibit 1019
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`
`
` A Little History
`
`5
`
`~ =
`
`-
`
`Q
`
`> I
`
`
`'\11mel_—oF
`
`Understanding Active Noise Cancellation
`
`Whohasbenefited most from all the effort and hundreds of millions of dollars
`that have so far been spenton developing active noise control technology? Perhaps
`the profession thathas so far benefited most from the invention ofactive noise contro]
`is the legal profession, which has been involved in a numberofpatent infringement
`law suits as well as the preparation of numerous patent applications. The number of
`patent applications has been increasing exponentially for the past 15 years and far
`exceeds the number of commercial applications of the technology. Nevertheless the
`many hundreds of patents granted indicate that many individuals and companies see
`the day eventually coming when active noise control systems will be widespread in
`industry and consumer goods.
`Whyis active noise cancellation of anyinterest to industry? It is becauseit offers
`a possible lower cost alternative to passive noise control for the control of low
`frequencynoise that has traditionally been difficult and expensive and in many cases
`not feasible to control, because of the long acoustic wavelengths involved. If only
`passive control techniquesare considered, these long wavelengths makeit necessary
`to use large mufflers and heavy enclosures for noise control, and very soft isolation
`systems and/orextensive structural dampingtreatmentfor vibration control.
`Manyofthe techniques describedin this book for active noise cancellation apply
`equally well
`to active vibration cancellation. In many cases the two types of
`disturbance are very closely related, as structures often radiate unwanted sound as a
`result oftheir vibration .
`The purposeof this book is to provide the reader with some insight into how
`active noise cancellation systems work. It is written so that most of it can be
`inderstood by a technically competent lay reader who has some understanding of
`loise control; however, there are some parts where the treatment goes’a bit deeper
`including a few mathematical equations) and these parts are intended for a reader
`vith a science or engincering degree. However, readers without the background
`ducation necessary to understand these parts can skip them andstill obtain a basic
`nderstanding of howactive noise cancellation works and for what applicationsit is
`uitable.
`
`2 EARLY HISTORY
`
`Ithoughthefirst observation of sound cancellation (using two Bell telephones) was
`ted by Thompson in 1878,it was notuntil 1930 that the French engineer, H. Coanda
`930) documented and then patented the idea of sound cancellation by destructive
`terference. He described an electro-acoustic system (microphone, amplifier and
`udspeaker) to generate a signal of opposite phase to the unwanted noise. A few
`ars later a Germanphysicist,P. Lueg (1933) described and Patented the idea of
`ing active sound cancellation as an alternative to passive control for low frequency
`und in a duct. His idea was to use a transducer (control source) to introduce a
`ondary (control) disturbance into the duct
`to cancel
`the existing (primary)
`‘turbance, thus resulting in an attenuation of the original sound as illustrated in
`sure 1,1, The cancelling disturbance wasto be derived electronically based upon a
`Exhibit 1019
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`Page 08 of 92
`
`1
`
`be\s
`
`ot*4!\t\!
`Myin|royi\ti‘t14\i\‘1i\t4ii!\t‘
`
`=--
`
`;!
`
`~
`m~
`
`Figure 1.1 Figures derived from Lueg’s patent (after P. Lueg, 1937)
`
`measurement of the primary disturbance. However, neither Coanda nor Lueg ever
`demonstrated a successful system and the technology lapsed into oblivion for wo
`decades. Oneoftheproblems with Lueg’s system wasthat there was no alowanee or
`the controller to adapt to system changes that would occuras a result of such
`things
`i
`erature changes.
`° Tafthe1850s the ideawas rekindled by aman named Olson (1953, 1956) —
`investigated possibilities for active sound cancellation in rooms, in eee
`headsets and earmuffs using feedback control. One of Olson spatents is illus ated
`i
`Figure 1,2. Unfortunately Olson’s system provided very limited attenuation overa
`verylimitedfrequencyrange andsufferedfrominstabilitydue 2 higheatnone
`for which the phase delays through the system exceeded 180 c Again, init eS
`the available electronic control hardware as er as inuations in control
`theory
`anions oz time asOlson was experimenting in his laboratory, W.
`Conover (1956) ofGeneral Electric demonstrated an active noise cancellationsystem
`fortransformernoise (seeFigure 1.3). Unfortunately the controllerhad to be: a
`manually and only reduced the sound over a very narrow angle subtended oe 7
`loudspeaker to the measurement microphone. Ofcourse, this system was — e 7
`impractical because it had to be continually adjusted manually due to changes
`
`ology
`
`from being commercially realised.
`
`i
`
`Exhibit 1019
`Page 08 of 92
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`Microphone4
`i— lacident
`z
`es Loudspeaker
`
`Batteries
`
`in controls
`oge
`
`Understanding Active Noise Cancellation
`Amplifier SoundpressureindB 3
`
`
`
`
`
`
`
`A Little History
`
`
`
`énvironmental conditions affecting the soundfield.It was alsooflimited benefit even
`when adjusted to its optimum performance due to the very localised area of reduced
`sound. Although there are now commercially available active noise control systems
`for electric power transformer noise control, a large number of loudspeakers and
`microphones (as well as vibration actuators on the transformer tank) are needed. Even
`then the achievement of a significant amount of global noise reduction is difficult
`(even though 15-20 dB is possible at the specific error microphonelocations).
`In the early 1980s, a numberofresearchers extended Olson's work to produce
`feedback systems that were more robust (Eghtesadiet al., 1983; Honget al., 1987). At
`the same time, Chaplin (1980) and Chaplin and Smith (1983) reported a waveform
`synthesis technique to cancel periodic noise and Warnaka.etal. (1981, 1984), Ross
`(1981) and Burgess (1981) developed a duct cancellation system based on adaptive
`filter theory.
`
`
`1.3 LATER HISTORY
`
`Since the original idea was conceivedin those very early days, the active control of
`sound as a technology has been characterised by transition: transition from a dream
`to practical implementation and froma laboratory experimentto mass production. This
`transition has taken a long time, partly because of the time it took to develop
`sufficiently powerful signal processing electronics, partly because of a lack of
`understanding of the physical principles involved and partly because of the multi-
`disciplinary nature of the technology, which combines a wide range of technical
`ets
`Control
`disciplines including Control, Signal Processing, Electronics, Acoustics and Vibration.
`speaker a f
`Being a collection of pieces, in which the strength ofthe chain is only as strong asits
`ty
`ti H
`Microphone
`weakestlink,it is little wonderthat the technology has been characterised by advances
`(Lj
`14
`Vv\
`that have comeinaseries of spurts rather than in a continuousflow.It was not until
`VAN
`
`the early 1990sthat regular implementationsofactive noise cancellation outsideof the
`laboratory were reported (Ericksson, 1990, 1991) and Wiseetal. (1992). Since that
` Power
`
`
`time numerouspractical implementations have been reported, including systems for
`Amplifier
`reducing helicopterand aircraft cabin noise.
`
`The resurgenceof interest in the technology is reflected in the exponentially
` Phase
`
`increasing numberofresearch publications onactive control: the numberof technical
`
`adjustor
`papers published on the topic since Coanda’s and Lueg's work in the 1930s has
`
`increased from approximately 240 before 1970 to 850 in the 1970sto 2,
`
` Amplitudeadjustor
`200 in the 1980s, and to over 4,000 in the 1990s.
`
`
` Signal
`Generator
`
`
`
`
`
`-2
`
`00
`.
`‘000
`200 300,,) 800,
`100
`3040 60
`Frequency in cycles per second
`i
`i
`’
`s elec
`i
`Figure 1.2 Olson's
`tronte sound absorber (reprinted with permission from, H. Olson,
`"Electronic sound absorber", Journal
`fe
`r
`‘
`ofthe AcousticalSoci
`fe
`Gipwicti, keiae /lainerhe no cietyofAmerica, 25, 1130-{ 136, 1953,
`
`20
`
`
`
`Transformer
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`
`
`8Figure 1,3 Conover’s active noise control system for transformer no. T
`
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`Exhibit 1019
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`Page 09 of 92
`
`1.4 CURRENT COMMERCIAL APPLICATIONS
`
`ise
`
`Althoughthere are many companiesand universities currently undertaking research
`and developmentofactive noise control applications, only a few applications have
`actually reached the commercialisation stage. Those applications include:
`
`Exhibit 1019
`Page 09 of 92
`
`

`

` Understanding Active Noise Cancellation
`
`
`
` A Little History
`system nderey as active noise cancellation generators (without
`sagen onceaulsemecil of complete systems can be brought in line with what
`core is prepared to pay, we must never lose sight of the fact ne there are
`i al limitations which makethe applicationofthe technology impractical in many
`: ae es. Examples of impractical applications are discussed in Chapter6.
`em the main reason for the lack of industrial application examples (as
`ea Ps mass produced consumer goods) is the seemingly excessive cost of such
`e llations, which mayeasily exceed the actual hardware cost by one or two orders
`orien itude The high costofthe labour componentis associated with the high level
`.vnainesritg expertise and high level of understanding of the principles of active
`Ee that are required ifthe installation is to be sdccessful. As active noise
`enirol expertise includes acoustics, signal processing, automatic aaTt
`Jectronics, the number of true experts throughout the world who are a i
`Feveloping and successfully installing active noise control systems is very 7ed.
`This also serves to limit the spread and commercialisation of the technology. A _
`to the cost of the labour componentis the unique nature of most problemsto wi Heh
`active noise control is applied, thus tending to preclude the use ofa generic im
`thatcan be installedbynon-expert technicians. In manycases,theunique nature ite
`problemsinvolved requires a large injeggion of development funds just to get
`to
`Shsleaaninexsiive,clever,commercialcontrolsystem,whichoe
`onstration stage.
`—_
`aselection ofsource and sensortransducersto satisfy most problems, and software :
`guide users in the correct choice andlocation of such transducers, does not a .
`The word “clever” used above todescribe the commercial control system,whic
`oes
`not yet exist, needs some explanation.Ifa controlleris to be useful to a wide rana7
`people, the effort involved in setting it up must be very small. This means
`7ne
`controller mustitselfbe controlled by a high level expert system or neural networ
`automatically sets input and output gains to maximise system aee
`convergence coefficients to optimise convergence speed and stabilitytrae :
`controlfilter type and weight numbers to optimise noise reduction, as well as ea 7
`coefficients and system ID algorithms,filter types and configurations to a
`controller performanceandstability. In addition, the controller should also isre a
`perform as an adaptive feedforward or adaptive feedback controller, be extenda a
`a large numberofchannels simply by adding together identical modules, and ih ‘
`advice on the suitability of feedforward control compared to feedback control ase
`on the quality of the available reference signal. Finally the aeWiatous
`during set-up (which shouldreally be aquestion/answer session) should
`be
`de
`based for maximum flexibility. The ability to connect a modem to the controller to
`allow remote access and interrogation of current performance and the state of
`transducers and other system componentsis also an important labour saving device.
`Recently,
`low cost active noise control hardware and software has become
`commercially available. As a result, the implementation complexity has beenreuce .
`Somewhat, putting it in the reach of people with an understanding and knowledge o
`
`low frequencytonal noise frommid-size propelleraircraft (many systems currently
`installed);
`headsets and ear muffs that actively reduce low frequency noiseat the ear (many
`thousands of units manufactured monthly);
`* helicopter cabin noise (by aclively controlling the transmission ofrotor and gearbox
`vibration throughthe supportstructure):
`*
`industrial air handling systems and large office building air conditioning systems
`(hundredsofinstalled systems, mainly in the USA);
`* diesel engine exhausts on stationary equipmentand buses (only a few systems
`installed); and
`* automobile engine vibration isolation (currently restricted to one or two models of
`vehicle in Japan).
`
`1.5 THE FUTURE
`
`Potential applicationsofactive noise cancellation that we could potentially see on a
`daily basis in the future are numerous and may include:
`* Consumergoods such as refrigerators, washing machines,air conditioners, lawn
`mowers, personal computers, range hoods, chain saws and vacuum cleaners;
`Cars - engine noise (both using loudspeakersin the passenger compartment and
`active vibration isolationof the engine) and road noise;
`Trucks and mining equipment - exhaust noise and cabin noise;
`:
`Air handling systems in industry arelikely to become more common candidates for
`active control - applied to ductwork carrying the noise:
`* Public phone booths;
`Aircraft and helicopter cabin noise control will become more widespread and will
`include aerodynamic noise as well as propeller noise;
`* Naval ships and pleasure boats; and
`¢ Diesel locomotives.
`laboratory
`Many of the applications mentioned above have seen successful
`demonstrations, but that seems to be where theystall.
`The mainreasonthatactive noise control systems haveyet to be commonly found
`in consumerproductsis their cost, A complete systemincludes a DSP and associated
`electronics as well as loudspeakers andmicrophones.Thecost of these components
`is acceptable to theaircraft industry but notcurrently to the automotive or consumer
`goods industry. Especially in the automotive industry, successful implementations
`have been developed (for low frequency engine and road noise, including active
`€ngine vibration isolation), but have not found widespread use because oftheir cost.
`Perhaps the key to more widespread application will be the integration of active noise
`control systems with existing hardware. For example the electronic signal processing
`for an automotive system could be done with the engine management computer
`(provided it was made sufficiently powerful) and use could be made of the stereo
`Exhibit 1019
`
`Page 10 of 92
`
`Exhibit 1019
`Page 10 of 92
`
`

`

`8
`
`Understanding Active Noise Cancellation
`
`acoustics and/or vibration, but only a superficial knowledge of signal processin
`control and electronics. However, much remains
`to be done to make i
`implementation ofactive noise control sufficiently simple thatit can be installed b
`the sametechniciansthatinstall passive noise control hardware.
`*
`In addition to the developmentof moreuserfriendlycontrol systems to implement
`applications that are already proven such as low frequencytonal noise control ina
`range ofsituations outdoors and indoors and low frequency random noisecontroljn
`ducts, current research is directed at extending the applications even further, It is
`expected that more effort will be focussed on feedback control systems for random
`noise, especially for passengersin aircraft. Effort will also be directed at extendingthe
`frequency rangeto higherlimits, particularly for the control of gearbox and engine
`noise in Naval vessels andaircraft. With this type of control, it will be necessary to
`implementthe active cancellation as close to the source as possible, probably using
`vibration actuatorsto controlthe vibration that is subsequently transmitted througha
`structure and radiated as noise,
`Unfortunately, the past history and credibility of active noise control as a viable
`alternative control measure has beentainted with a minority of commercial companies
`making prematurepublic claims regarding its application, which werefar in excess of
`what was realistic (or what they could deliver). This has resulted in the technology
`being viewed with suspicion by key manufacturers of particular mass market products
`that have potential to benefit from the judicious application of active noise control
`technology. The field has also been tainted by the unscrupulous patenting by some
`companies of technology that had been published by other unrelated researchers in
`journal papers or consulting reports years beforethefiling of the subject patents. This
`unscrupulous patenting is often followed up with equally unscrupulous threats of
`indefensible legal action against users of the technology. Unfortunately,this activity
`is still continuing in some cases,andit is very likely that manyofthe current 800 to
`1000 patents relevantto active noise or vibration control can b