UNITED STATES PATENT AND TRADEMARK OFFICE
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
`
`GOOGLE LLC,
`
`Petitioner
`
`v.
`
`JAWBONE INNOVATIONS, LLC,
`
`Patent Owner
`
`Case IPR2022-01124
`U.S. Patent No. 11,122,357
`______________________
`
`Declaration of Shauna L. Wiest Regarding McCowan
`
`Page 1 of 78
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`GOOGLE EXHIBIT 1007
`
`

`

`Declaration of Shauna L. Wiest
`
`
`I, Shauna L. Wiest, state and declare as follows:
`
`Introduction
`
`
`
`I.
`
`1.
`
`I have prepared this Declaration in connection with Google LLC’s
`
`(“Petitioner”) Petition for Inter Partes Review of U.S. Patent No. 11,122,357,
`
`which I understand will be filed concurrently with this Declaration.
`
`2.
`
`I am currently a senior research analyst with the Research &
`
`Information Services team at Finnegan, Henderson, Farabow, Garrett & Dunner,
`
`LLP, located at 901 New York Avenue, NW, Washington, DC 20001-4413.
`
`3.
`
`I am over eighteen years of age, and I am competent to make this
`
`Declaration. I make this Declaration based on my own personal knowledge, and
`
`my knowledge of library science practices.
`
`4.
`
`I earned a Master of Science in Library Science degree from the
`
`University of North Carolina at Chapel Hill in 1999, and a Bachelor of Arts in
`
`Political Science degree from the University of California at San Diego in 1989.
`
`I have worked as a law librarian for over twenty years. I have been employed in
`
`the Research & Information Services Department at Finnegan, Henderson,
`
`Farabow, Garrett & Dunner, LLP since 2021. Before that, from 2000-2015, I
`
`was employed as a Law Librarian at Stoel Rives LLP, and from 2015-2016, I
`
`was employed as a Competitive Intelligence Specialist for Nossaman LLP.
`
`
`
`2
`
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`
`II.
`
`Standard Library Practice for Receiving, Cataloging, and Making
`Materials, Including Serial Publications, Publicly Available
`
`Declaration of Shauna L. Wiest
`
`
`5.
`
`I have knowledge of and experience with standard library practices
`
`regarding the receipt, cataloging, shelving, and making materials, including
`
`serial publications, available to the public. I am fully familiar with and have
`
`knowledge of and experience with the Machine-Readable Cataloging (MARC)
`
`system, an industry-wide standard that libraries use to catalog materials.
`
`6.
`
`The MARC system was developed during the 1960s to standardize
`
`bibliographic records so they could be read by computers and shared among
`
`libraries. By the mid-1970s, MARC had become the international standard for the
`
`storage of bibliographic data and cataloguing. It is still used today. Many libraries
`
`provide public access to their MARC records via the Internet and/or their electronic
`
`cataloging systems at the library. In a MARC record, each field provides specific
`
`information about the cataloged item, including how materials are held and made
`
`available to the public.
`
`III. Serial Publications
`
`7.
`
`A serial publication, often known as a “journal,” is a resource that
`
`is issued in successive parts and has no predetermined conclusion. These
`
`successive parts are commonly referred to as “issues,” and each issue is usually
`
`chronologically numbered and dated. The presence of enumeration, years of
`
`
`
`3
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`Declaration of Shauna L. Wiest
`
`
`coverage, and/or other chronological information also indicates a serial
`
`publication.
`
`8.
`
`There are significant differences between cataloging finite resources
`
`(books/monographs) and continuing resources (serials). For serials, the catalog
`
`record provides information about the serial as a whole, including the first or earliest
`
`available issue. It also provides information as to holdings – the volumes and issues,
`
`with dates, received by the library and made available to the public. In serials
`
`cataloging, there are identifying characteristics unique to serials that are slightly
`
`different from monographs (books). The issue date for a print serial publication, for
`
`example, generally appears on the cover (front or back), the masthead page, the title
`
`page (if any), the table of contents page(s), or on the pages of the individual articles
`
`contained in the issue. More information regarding the unique aspects of cataloguing
`
`serials can be found at this link: https://www.loc.gov/aba/pcc/conser/scctppt/Basic-
`
`2014/Basic-Trainee-Mannual.pdf
`
`IV. MARC Records
`
`9.
`
`The MARC record system uses a specific three-digit numeric code
`
`(from 001-999) to identify each field in a catalog record. For example, field tag 008
`
`provides the six-digit date the item was catalogued (Date entered on file). The first
`
`six characters of field tag 008 are always in the “YYMMDD” format. Field tag 022
`
`provides the International Standard Serial Number (ISSN), a unique identification
`
`
`
`4
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`Declaration of Shauna L. Wiest
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`
`number assigned to serial publications (continuing resource). Field tag 245 identifies
`
`the full title statement for the work and field tag 260 identifies the place of
`
`publication, name of publisher, and copyright date of the publication. Field tag 362
`
`identifies the numbering to be used for chronological cataloguing of individual
`
`issues of continuing resources (serials). The designations within field tag 362
`
`determine at what point in time the serial began, which guides how issues are
`
`checked in, processed, and added to the library’s main collection. Finally, the 9XX
`
`field tags denote local holdings information for the resource.
`
`10.
`
` Based on standard library practice, when a library receives an
`
`item, it stamps (or labels) the item with the library name and often with a date
`
`that is within a few days or weeks of receipt. Next, the library will catalog the
`
`item within a matter of a few days or weeks of receiving it.
`
`11. Generally, after an item is cataloged, the public may access the
`
`item by searching a catalog, browsing the library shelves, and either requesting
`
`or electronically accessing the item from the library. Standard library practice is
`
`to make the item available to the public within a few days or weeks of cataloging
`
`it.
`
`V.
`
`Print Holdings and MARC Records for McCowan
`
`12. As detailed below, I have reviewed the print public holdings
`
`information and Library of Congress and Iowa State University of Science and
`
`
`
`5
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`Declaration of Shauna L. Wiest
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`
`Technology MARC records for Iain A. McCowan, Darren C. Moore, and S.
`
`Sridharan, “Near-field Adaptive Beamformer for Robust Speech Recognition,”
`
`Digital Signal Processing, January 2002, Vol. 12, No. 1, pages 87-106 (ISSN
`
`1051-2004) (“McCowan”). Exhibit 1007 to the concurrently filed Petition is a
`
`true and accurate copy of McCowan.
`
`13.
`
`Appendix A to this declaration is a true and accurate copy of the print
`
`journal cover, title pages, table of contents, and library date stamp for the issue of
`
`Digital Signal Processing containing McCowan held by the Library of Congress.
`
`Appendix A also includes pages 87 to 106 of this issue, which is the article titled
`
`“Near-field Adaptive Beamformer for Robust Speech Recognition” (McCowan). The
`
`date stamp for this issue indicates that McCowan was received by the Library of
`
`Congress on February 19, 2002. The print journal cover provides directional
`
`information so that members of the interested public could access the print issue
`
`containing McCowan at Call Number TK 5102.5 .D4463 Set 1 with Bar Code 0 020
`
`814 014 0 within a matter of a few days or weeks of February 19, 2002.
`
`14. Based on the information in Appendix A, it is clear that the issue of
`
`Digital Signal Processing containing McCowan was received by the Library of
`
`Congress on or before February 19, 2002. Based on standard library practice,
`
`McCowan would have been processed and catalogued by the Library of Congress
`
`within a matter of a few days or weeks of February 19, 2002.
`
`
`
`6
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`
`Declaration of Shauna L. Wiest
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`15. Accordingly, McCowan would have been made available to the public
`
`within a few days or weeks of being checked-in and catalogued. Members of the
`
`interested public could have accessed McCowan by browsing the Library of
`
`Congress shelves or by searching the Library’s catalog within a few days or weeks
`
`of February 19, 2002.
`
`16.
`
` Appendix B to this declaration is a true and accurate copy of the
`
`Library of Congress MARC record for its holdings of the serial publication Digital
`
`Signal Processing containing McCowan, which was downloaded
`
`from
`
`https://lccn.loc.gov/91650983/marcxml on April 5, 2022.
`
`17. Appendix C to this declaration is a true and correct copy of the Library
`
`of Congress public catalog record for its copy of Digital Signal Processing
`
`containing McCowan, including holdings and location information, which was
`
`downloaded
`
`from
`
`https://catalog.loc.gov/vwebv/holdingsInfo?searchId=17671&recPointer=0&recCo
`
`unt=25&searchType=2&bibId=11390503 on April 5, 2022.
`
`18. Appendix D to this declaration is a true and accurate copy of the print
`
`journal cover, title pages, table of contents, and library date stamp for the issue of
`
`Digital Signal Processing containing McCowan held by the Iowa State University of
`
`Science and Technology Library. Appendix D also includes pages 87 to 106 of this
`
`issue, which is the article titled “Near-field Adaptive Beamformer for Robust Speech
`
`
`
`7
`
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`Declaration of Shauna L. Wiest
`
`
`Recognition” (McCowan). The date stamp for this issue indicates that McCowan was
`
`received by the Iowa State University of Science and Technology Library on
`
`February 18, 2002. The print journal cover provides directional information so that
`
`members of the interested public could access the print issue containing McCowan
`
`at Call Number TK 5102.5 .D4463 within a matter of a few days or weeks of
`
`February 18, 2002.
`
`19. Based on the information in Appendix D, it is clear that the issue of
`
`Digital Signal Processing containing McCowan was received by the Iowa State
`
`University of Science and Technology Library on or before February 18, 2002.
`
`Based on standard library practice, McCowan would have been processed and
`
`catalogued by the Iowa State University of Science and Technology Library within
`
`a matter of a few days or weeks of February 18, 2002.
`
`20. Accordingly, McCowan would have been made available to the public
`
`within a few days or weeks of being checked-in and catalogued. Members of the
`
`interested public could have accessed McCowan by browsing the Iowa State
`
`University of Science and Technology Library shelves or by searching the Library’s
`
`catalog within a few days or weeks of February 18, 2002.
`
`21. Appendix E to this declaration is a true and accurate copy of the Iowa
`
`State University of Science and Technology Library MARC record for its holdings
`
`of the serial publication Digital Signal Processing containing McCowan, which was
`
`
`
`8
`
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`
`downloaded
`
`from
`
`Declaration of Shauna L. Wiest
`
`https://iowa-primo.hosted.exlibrisgroup.com/primo-
`
`explore/sourceRecord?vid=01IASU&docId=01IASU_ALMA21233591260002756
`
`on May 10, 2022.
`
`22. Appendix F to this declaration is a true and correct copy of the Iowa
`
`State University of Science and Technology Library public catalog record for its
`
`copy of Digital Signal Processing containing McCowan, including holdings and
`
`location
`
`information, which was
`
`downloaded
`
`from
`
`https://iowa-
`
`primo.hosted.exlibrisgroup.com/permalink/f/12tutg/01IASU_ALMA21233591260
`
`002756 on April 20, 2022.
`
`23. The Library of Congress MARC record (Appendix B) for the serial
`
`publication Digital Signal Processing containing McCowan confirms the fixed data
`
`elements of MARC field tag 008 as 900620c19919999mnubrp0a0engc. As
`
`discussed above, the first six characters “900620” are in typical “YYMMDD”
`
`format and indicate that the serial publication Digital Signal Processing was
`
`catalogued by the Library of Congress on June 20, 1990. The publication status code
`
`“c” appearing in MARC field tag 008 refers to “continuing resource currently
`
`published” indicating that Digital Signal Processing began publication in 1991 and
`
`is a continuing published resource.
`
`24. The Library of Congress MARC record field tag 022 denotes the unique
`
`International Standard Serial Number (ISSN) for Digital Signal Processing as 1051-
`
`
`
`9
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`Declaration of Shauna L. Wiest
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`2004. The Library of Congress MARC record field tag 245 denotes the title and
`
`statement of responsibility for the work as “Digital Signal Processing.”
`
`25. The Library of Congress MARC record field tag 362 provides a
`
`chronological designation of a continuing (serial) resource. In this MARC record for
`
`Digital Signal Processing the sequential serial designation begins with Volume 1,
`
`no. 1 (Jan. 1991)- with no end date noted.
`
`26. Finally, the Library of Congress MARC record field tags 984 and 991
`
`identify the holdings, location, and call number for its copy of Digital Signal
`
`Processing containing McCowan. The MARC record lists this information as:
`
`General Collection, Call Number TK5102.5 .D4463, Serials Location, with holdings
`
`beginning with the issue dated January 9, 2001. This information confirms that the
`
`journal issue of Digital Signal Processing containing McCowan is publicly available
`
`and held in the General Collection at Call Number TK5102.5 .D4463.
`
`27. The Library of Congress’s public catalog record for its copy of Digital
`
`Signal Processing (Appendix C) sets forth the holdings and onsite location
`
`information for members of the public seeking the print issue containing McCowan.
`
`The public catalog record indicates that the print issue containing McCowan should
`
`be requested in the Jefferson or Adams Building Reading Rooms and is contained
`
`within holdings v.3-v.12:no.1 (1993-2002:Jan.) at Call Number TK5102.5 .D4463.
`
`
`
`10
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`
`
`Declaration of Shauna L. Wiest
`
`28. The Iowa State University of Science and Technology Library MARC
`
`record (Appendix E) for the serial publication Digital Signal Processing containing
`
`McCowan confirms the fixed data elements of MARC field tag 008 as
`
`900620c19919999mnubr1p0a0engd. As discussed above, the first six characters
`
`“900620” are in typical “YYMMDD” format and indicate that the serial publication
`
`Digital Signal Processing was catalogued by the Iowa State University of Science
`
`and Technology Library on June 20, 1990. The publication status code “c” appearing
`
`in MARC field tag 008 refers to “continuing resource currently published”
`
`indicating that Digital Signal Processing began publication in 1991 and is a
`
`continuing published resource.
`
`29. The Iowa State University of Science and Technology Library MARC
`
`record field tag 999 (including the AVA field tag) identifies the local holdings,
`
`location, and call number for its copy of McCowan. The AVA field tag in this MARC
`
`record lists the holdings information as: ##$0990008738310102756$822233
`
`591250002756$a01IASU_INST$bPARKS$cStorage Building$dTK5102.5 D4463
`
`$echeck_holdings$jSGEN$k0$p1$qPARKS$tv. 4 (1994)-v. 15 (2005). This
`
`information confirms that the print issue of Digital Signal Processing containing
`
`McCowan, is available and held in the PARKS Storage Building at Call Number
`
`TK5102.5 .D4463, with holdings beginning with Volume 4 (1994) through Volume
`
`15 (2005).
`
`
`
`11
`
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`
`
`Declaration of Shauna L. Wiest
`
`30. The Iowa State University of Science and Technology Library’s public
`
`catalog record for its copy of Digital Signal Processing (Appendix F) sets forth the
`
`public holdings and onsite location information for members of the public seeking
`
`the print issue containing McCowan. The public catalog record indicates that the
`
`2002 Bound Issue (volume 12) of Digital Signal Processing containing McCowan,
`
`is publicly available and held in the PARKS Storage Building at Bar Code
`
`32792018902886 at Call Number TK5102.5 .D4463.
`
`31. Based on this evidence, it is my opinion that Exhibit 1007 is an
`
`authentic document, which would have been made publicly available and publicly
`
`accessible within a few days or weeks of February 19, 2002.
`
`VI. Conclusion
`
`32.
`
`In signing this Declaration, I understand it will be filed as evidence
`
`in a contested case before the Patent Trial and Appeal Board of the United States
`
`Patent and Trademark Office. I understand I may be subject to cross-
`
`examination in this case and that cross-examination will take place within the
`
`United States. If cross-examination is required of me, I will appear for cross-
`
`examination within the United States during the time allotted for cross-
`
`examination.
`
`33.
`
`I declare that all statements made herein of my knowledge are true, that
`
`all statements made on information and belief are believed to be true, and that these
`
`
`
`12
`
`Page 12 of 78
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`

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`Declaration of Shauna L. Wiest
`
`
`statements were made with the knowledge that willful false statements and the like
`
`so made are punishable by fine or imprisonment, or both, under Section 1001 of Title
`
`18 of the United States Code.
`
`
`
`
`
`
`
`Executed on June 14, 2022.
`
`
`
`Shauna L. Wiest
`
`13
`
`Page 13 of 78
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`

`

`Appendix A
`Appendix A
`
`Page 14 of 78
`
`

`

`A
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`Page 15 of 78
`
`

`

`
`
`DIGITALSIGNALPROCESSING
`
`
`
`] Page 16 of 78
`
`12
`
`UNL
`
`raAY
`
`Page 16 of 78
`
`

`

`owoyoy
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`L_
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`A Review Journa Seih
`
`
`
`Editors
` Jim Sch ‘oeder
`
`Joe Campbell
`
`
`- ‘
`I!
`
`f
`
`
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`weenie ese
`
`Page 17 of 78
`
`Page 17 of 78
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`

`

`Digital
`oI
`Processing
`
`A Review Journal
`
`Editors
`
`Jim Schroeder
`SPRI/CSSIP
`Adelaide, SA, Australia
`E-mail: schroeder@cssip.edu.au
`
`Joe Campbell
`M.LT. Lincaoin Laboratory
`Lexington, Massachusetts
`E-mail: j.campbell@icee.org
`
`Editorial Board
`
`Maurice Bellanger
`CNAM
`Paris, France
`
`Robert E. Bogner
`University of Adelaide
`Adelaide, SA, Australia
`Johann F. Bohme
`Auhr-Universitat Bochum
`Bochum, Germany
`James A. Cadzow
`Vanderbilt University
`Nashville, Tennessee
`G. Clifford Carter
`NUWC
`Newport, Rhode island
`A. G. Constantinides
`imperial College
`London, England
`Petar M. Djuric
`Stale University of New York
`Stony Brook, New York
`Anthony D. Fagan
`University College Dublin
`Dublin, treland
`SadaokiFurui
`Tokyo Institute of Technology
`Tokyo, Japan
`
`John E. Hershey
`General Electric Company
`Schenectady, New York
`B. R. Hunt
`University of Arizona
`Tucson, Arizona
`JamesF. Kaiser
`Duke University
`Durham, North Carolina
`
`R. Lynn Kirlin
`University of Victoria
`Victoria, British Columbia, Canada
`Ercan Kuruoglu
`Istituto oi Elaborazione della Informazione
`Ghezzano,Italy
`MeemongLee
`Jet Propulsion Laboratory
`Pasadena, California
`Petre Stoica
`Uppsala University
`Uppsala, Sweden
`Mati Wax
`Wavion, Ltd
`Yoqneam, !sreal
`Rao Yarlagadda
`Oklahoma State University
`Stillwater, Okiahoma
`
`Cover photo, Lower path directivily pattern at SOOU Hz. See the article by McCowan, Moore, and Sridharan in
`this issue
`
`Page 18 of 78
`
`Page 18 of 78
`
`

`

`
`
`
`Cennky OF OnGRS
` wo
`FEB 1
`&
`2002
`
`
`Copy.
`Lerrant DEO
`
`
`pi
`
`Digital Signal Processing
`
`Volume 12, Number 1, January 2002
`
`© 2002 Elsevier Science (USA)
`
`All Rights Reserved
`
`No part of this publication may be reproduced or transmitted in any form or by any means,electronic or mechanical, including photocopy,
`recording, or any information storage and retrieval system, without permission in writing from the Publisher. Exceptions: Explicit permission
`from Academic Press is not required to reproduce a maximum oftwo figures or tables from an Academic Pressarticle in another scientific or
`research publication providedthat the material has not been credited to another source and thatfull credit to the Academic Pressarticle is
`given. In addition, authors of work contained herein need not obtain permission in the following cases only: (1) to use their original figures or
`tablesin their future works; (2} to make copiesof their papers for usein their classroom teaching; and (3) to include their papers as part oftheir
`dissertations.
`The appearanceof the codeat the bottom of thefirst page of an article in this journal indicates the Publisher's consentthat copies of the
`article may be made for personalorinternal use, or for the personal orinternal use of specific clients. This consent is given on the condition,
`however,
`that the copier pay the stated per copy fee through the Copyright Clearance Center,
`Inc. (222 Rosewood Drive, Danvers,
`Massachusetts 01923), for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent doesnot extend to
`other kinds of copying, such as copying for generaldistribution, for advertising or promotional purposes, for creating new collective works, or for
`resale, Copyfees for pre-2002 articles are as shown onthearticletitle pages: if no fee code appearsonthetitle page, the copy fee is the same
`as those for currentarticles.
`
`1051-2004/02 $35.00
`MADEIN THE UNITED STATES OF AMERICA
`This journalis printed on acid-free paper.
`
`©
`DIGITAL SIGNAL PROCESSING(ISSN 1051-2004)
`Published quarterly by Elsevier Science.
`Editorial and Production Offices: 525 8 Street, Suite 1900, San Diego, CA 92101-4495
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`Digital Signal Processing 12, 87-106 (2002)
`doi:10.100G6/dspr.2001.0414,available online at http://www.idealibrary.com on 1 D E mL
`
`®
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`This material may be protected by Copyright law (Title 17 U.S. Code)
`
`Near-field Adaptive Beamformer for Robust
`Speech Recognition
`
`Iain A. McCowan, Darren C. Moore, and S. Sridharan
`
`Speech Research Laboratory, RCSAVT, School of EESE, Queensland University
`of Technology, GPO Box 2434, Brisbane QLD 4001, Australia
`E-mail: iain@ieee.org; moore@idiap.ch; s.sridharan@qut.edu.au
`
`McCowan, I. A., Moore, D. C., and Sridharan, S., Near-field Adaptive
`Beamformer for Robust Specch Recognition, Digital Signal Processing 12
`(2002) 87-106.
`
`This paper investigates a new microphone array processing technique
`specifically for the purpose of speech enhancement and recognition. The
`main objective of the proposed technique is to improve the low frequency
`directivity of a conventional adaptive beamformer, as low frequency per-
`formanceis critical in speech processing applications. The proposed tech-
`nique, termed near-field adaptive beamforming (NFAB), is implemented
`using the standard generalized sidelobe canceler (GSC) system structure,
`wherea near-field superdirective (NFSD) beamformeris used as the fixed
`upper-path beamformer to improve the low frequency performance. In ad-
`dition, to minimize signal leakage into the adaptive noise canceling path for
`near-field sources, a compensation unit is introduced prior to the blocking
`matrix. The advantage of the techniqueis verified by comparing the direc-
`tivity patterns with those of conventional filter-sum, NFSD, and GSC sys-
`tems. In speech enhancement and recognition experiments, the proposed
`technique outperforms the standard techniques fora near-field source in
`adverse noise conditions.
`© 2002 ElsevierScience (USA)
`Key Words: microphone array; beamforming; near-field; adaptive; su-
`perdirectivity; speech recognition.
`
`INTRODUCTION
`1.
`==
`
`Currently, much research is being undertaken to improve the robustness of
`speech recognition systems in real environments. This paper focuses on the
`use of a microphone array to enhance the noisy input speech signal prior to
`recognition. While the use of microphonearrays for speech recognition has been
`studied for some time by a numberof researchers, a persistent problem has been
`the poor low frequencydirectivity of conventional beamforming techniques with
`87
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`© 2002 Elsevier Science (USA)
`All rights reserved.
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`Digital Signal Processing Vol. 12, No. 1, January 2002
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`practical array dimensions. Low frequency performanceis critical for speech
`processing applications, as significant speech energy is located below 1 kHz.
`By explicitly maximizing the array gain, superdirective beamforming tech-
`niques are able to achieve greaterdirectivity than conventional techniques with
`closely spaced sensor arrays [1]. This directivity generally comes at the expense
`of a controlled reduction in the white noise gain of the array. Recent work has
`demonstrated the suitability of superdirective beamforming for speech enhance-
`ment and recognition tasks [2, 3]. By employing a spherical propagation model
`in its formulation, rather than assuminga far-field model, near-field superdirec-
`tivity (NFSD) succeeds in achieving high directivity at low frequencies for near-
`field speech sources in diffuse noise conditions [4]. In previous work, near-field
`superdirectivity has been shownto lead to good speech recognition performance
`in high noise conditionsfor a near-field speaker[5].
`Superdirective techniques are typically formulated assuming a diffuse noise
`field. While this is a good approximation to many practical noise conditions,
`further noise reduction would result from a more accurate model of the
`actual noise conditions during operation. Adaptive array processing techniques
`continually update their parameters based on thestatistics of the measured
`input noise. The generalized sidelobe canceler (GSC) [6] presents a structure
`that can be used to implement a variety of adaptive beamformers. A block
`diagram of the basic GSC system is shown in Fig. 1. The GSC separates
`the adaptive beamformer into two main processing paths—a standard fixed
`beamformer, w, with L constraints on the desired signal response, and an
`adaptive path, consisting of a blocking matrix, B, and a set of adaptive filters, a.
`As the desired signal has been constrained in the upper path, the lower path
`filters can be updated using an unconstrained adaptive algorithm, such as the
`least-mean-square (LMS)algorithm.
`While the theory of adaptive techniques promises greater signal enhance-
`ment, this is not always the case in real situations. A common problem with
`the GSC system is leakage of the desired signal through the blocking matrix,
`resulting in signal degradation at the beamformer output. This is particularly
`problematic for broadband signals, such as speech, and especially for speech
`recognition applications where signal distortionis critical.
`In this paper we propose a system that is suited to speech enhancement in a
`practical near-field situation, having both the good low frequency performance
`of near-field superdirectivity and the adaptability of a GSC system, while taking
`
`
`
`FIG. 1. Generalized sidelobe canceler structure.
`
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`McCowan, Moore, and Sridharan: Near-field Adaptive Beamformer
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`89
`
`care to minimize the problem of signal degradation for near-field sources.
`We begin by formulating a concise model for near-field sound propagation in
`Section 2. This model is then used in Section 3 to develop the proposed near-
`field adaptive beamforming (NFAB) technique. To demonstrate the benefit of
`the technique over existing methods, an experimental evaluation assessing
`directivity patterns, speech enhancement performance, and speech recognition
`performanceis detailed in Sections 4 and 5.
`
`2. NEAR-FIELD SOUND PROPAGATION MODEL
`
`a I
`
`n sensor array applications, a succinct means of characterizing both the
`array geometry and thelocation of a signal sourceis via the propagation vector.
`The propagation vector concisely describes the theoretical propagation of the
`signal from its source to each sensor in thearray. In this section, we develop an
`expression for the propagation vector of a sound source locatedin the near-field
`of a microphone array using a spherical propagation model. This expression is
`then used in the formulation of the proposed near-field adaptive beamformer in
`the following sections.
`Many microphone array processing techniques assume a planar signal
`wavefront. This is reasonable for a far-field source, but when the desired
`source is close to the array a more accurate spherical wavefront model must
`be employed. For a microphonearray of length L, a source is considered to be
`in the near-field if r <2L7/A, where ris the distance to the source and 4 is the
`wavelength.
`Wedefine the reference microphoneas theorigin of a 3-dimensional vector
`space, as shown in Fig. 2. The position vector for a source in direction (6;, ¢s),
`at distance r, from the reference microphone, is denoted p, andis given by:
`
`cos @; sin ds
`
`cos ds
`
`Pp; ="s[% Y- Z]|sind, sings| . (1)
`
`
`
`(i =1,...,N), are similarly
`The microphone position vectors, denoted as p;
`defined. The distance from the source to microphone/ is thus
`
`d; = Ps — pill,
`
`(2)
`
`where|| || is the Euclidean vector norm.
`In such a model, the differences in distance to each sensor can be significant
`for a near-field source, resulting in phase misalignment across sensors. [The
`difference in propagation time to each microphonewith respect to the reference
`microphone(i = 1) is given by
`
`j=
`
`
`dj —d,
`c
`
`5
`
`(3)
`
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`Digital Signal Processing Vol. 12, No. 1, January 2002
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` reference
`
`microphone
`
`“
`
`&
`x
`
`microphonei
`Bi
`
`FIG. 2. Near-field propagation model.
`
`where c = 340 ms! for sound. In addition, the wavefront amplitude decays at a
`rate proportional to the distance traveled. The resulting amplitude differences
`across sensors are negligible for far-field sources, but can be significant in
`the near-field case. The microphone attenuation factors, with respect to the
`amplitude on the reference microphone, are given by
`
`1
`a= a
`d;
`
`(4)
`
`Thus, if x1(/) is the desired source at the reference microphone, the signal on
`the ith microphoneis given by
`
`xi(f) sajxi(fyel?™,
`
`(5)
`
`Consequently, we define the near-field propagation vector for a source at
`distance r and direction (0, @) as
`
`d(fr6.e= [aye27" oe FOF ayeJ2thtw)
`
`(6)
`
`3. NEAR-FIELD ADAPTIVE BEAMFORMING
`SS
`
`The proposed system structure is shown in Fig. 3. The objective of the
`proposed technique is to add the benefit of good low frequency directivity
`to a standard adaptive beamformer, as low frequency performanceis critical
`in speech processing applications. The upper path consists of a fixed near-
`field superdirective beamformer, while the lower path contains a near-field
`compensation unit, a blocking matrix and an adaptive noise cancelingfilter.
`The principal componentsof the system are discussed in the following sections.
`
`
`
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`McCowan, Moore, and Sridharan: Near-field Adaptive Beamformer
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`91
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`Fixed
`
`
`NFSD
`
`Beamformer
`
`
`
`
`Blocking
` Near-field
`
`Matrix
`
`FIG. 3. Near-field adaptive beamformer.
`
`Section 3.1 gives an explanation of the near-field superdirective beamformer.
`Section 3.2 proposes the inclusion of a near-field compensation unit in the
`adaptive sidelobe canceling path and examines its effect on reducing signal
`distortion at the output. Once this near-field compensation has been performed,
`a standard generalized sidelobe canceling blocking matrix and adaptive filters
`can be applied to reduce the output noise power, as discussed in Section 3.3.
`
`3.1. Near-field Superdirective Beamformer
`Superdirective beamforming techniques are based upon the maximization of
`the array gain, or directivity index. The array gain is defined as the ratio of
`output signal-to-noise ratio to input signal-to-noise ratio and for the general
`case can be expressed in matrix notation as [1]
`
`_ wif) PCfyw(f)
`= wi PFQAWU)
`Cf)=—
`
`whe