Japanese  English
Nobutaka ITO (Ph.D.)
Research Scientist
Communication Science Laboratories, NTT Corporation, Japan
nobutaka.itou.st(at)hco.ntt.co.jp
Visiting Industrial Fellow
University of Cambridge
Links
Short bio
Dr. Nobutaka Ito was born in Ibaraki, Japan in 1983. He received the B.E. degree in engineering from the University of Tokyo, Tokyo, Japan in 2007 and the M.E. and the Ph.D. degrees in information science and technology from the University of Tokyo, Tokyo, Japan in 2009 and 2012, respectively.
In 2012, he joined Communication Science Laboratories, NTT Corporation, Kyoto, Japan as a Researcher, and in 2017 became a Research Scientist. Since March 2019, he has also been with the Department of Engineering, the University of Cambridge, Cambridge, United Kingdom as a Visiting Industrial Fellow. His research interests include source separation, speech enhancement, microphone arrays, array signal processing, acoustic signal processing, and image processing.
He will serve as a Member of IEEE Audio and Acoustic Signal Processing (AASP) Technical Committee (TC) from 2020, and has
served as a Committee Member of the fourth/fifth/sixth/seventh communitybased Signal Separation Evaluation Campaign (SiSEC2013/2015/2016/2018).
He made a central contribution to NTT's automatic speech recognition (ASR) system that achieved the best performance in the CHiME3 challenge, especially by
developing the key frontend technique called a complex Gaussian mixture model (cGMM). He received the Best Paper Award of the 16th International Workshop on Acoustic Signal Enhancement (IWAENC) held in Tokyo in 2018, the fifth IEEE Signal Processing Society Japan Chapter Student Paper Award in 2011, JSIAM Transactions Best Paper Award of the Japan Society for Industrial and Applied Mathematics in 2009, the 10th Itakura Prize Innovative Young Researcher Award of the Acoustical Society of Japan in 2015, Awaya Prize Young Researcher Award of the Acoustical Society of Japan in 2018, the Best Paper Award Honorable Mention of
IEEE Automatic Speech Recognition and Understainding Workshop (ASRU 2015) held in Scottsdale in 2015, Senior Vice President's Award of Science and Core Technology Laboratory Group, NTT Corporation in 2017, Vice President's Award of Communication Science Laboratories, NTT Corporation in 2014, 2016, and 2019, etc. Dr. Ito is a Member of IEEE and the Acoustical Society of Japan.
Research Interests
Source separation, speech enhancement, microphone arrays, array signal processing, acoustic signal processing, image processing
 Source separation
 FastFCA: Fast method for separating more sources than microphones
(joint diagonalizability constraint [Ito+2018IWAENC], generalized eigenvalue decomposition [Ito+2018EUSIPCO], multiplicative updates [Ito+2018GlobalSIP], application to multichannel nonnegative matrix factorization [Ito+2019ICASSP])
 Source location clustering based on directional statistics (cBMM [Ito+2018SpringerTextbook], cACGMM [Ito+2016EUSIPCO], cGMM [Ito+2014IWAENC], permmutationfree cGMM [Azcarreta+2018ICASSP], noisy cGMM [Ito+2018EUSIPCO])
 Noise reduction
 Noise reduction for robust automatic speech recognition (ASR)
[Yoshioka+2015ASRU]
 Diffure noise suppression exploiting symmetry (crystal arrays [Ito+2011IEEETrans.ASLP], imaginary part method [Ito+2010ICASSP], matrix subspace [Ito+2015J.Sig.Pro.Sys.])
 Diffuse noise robust multiple source localization [Ito+2012INRIA]
 Composite noise reduction
 Overall optimization of linear prediction based dereverberation and symmetrybased diffuse noise reduction [Ito+2014ICASSP]
 Overall optimization of linear prediction based dereverberation and clusteringbased source separation [Ito+2014IWAENC]
 Source counting
 Joint source separation and counting in reverberant environments [Ito+2014J.IEICE]
 Speaker diarization
 Probabilistic spatial dictionary (fundamental technique [Ito+2017ICASSP], spatiotemporal NMF [Ito+2018ICASSP])
 Image processing
 Image feature extraction based on complex moments [Ito+2008J.JSIAM]
Background
 2003.4  2007.3 B.E. at the University of Tokyo, Japan
 2007.4  2009.3 M.E. in Information Science and Technology at the University of Tokyo, Japan
 2009.4  2012.3 Ph.D. in Information Science and Technology at the University of Tokyo, Japan
 2009.9  2010.8 Student of Collège Doctoral FrancoJaponais (Visitor to Dr. Rémi Gribonval and Dr. Emmanuel Vincent, INRIA Rennes, France)
 2010.4  2012.3 Research Fellow of the Japan Society for the Promotion of Science, Japan
 2010.9  2010.10 Visitor to Dr. Rémi Gribonval and Dr. Emmanuel Vincent, INRIA Rennes, France
 2012.1  2012.3 ditto
 2012.4  2017.6 Researcher, NTT Communication Science Laboratories, NTT Corporation, Japan
 2017.7  Present Research Scientist, NTT Communication Science Laboratories, NTT Corporation, Japan
 2019.3  Present Visiting Industrial Fellow, University of Cambridge, United Kingdom (Visitor to Prof. Simon Godsill)
Academic Activities
 Committee member, CommunityBased Signal Separation Evaluation Campaign (SiSEC) (2013 )
 Invited talk at EUSIPCO2017 (2017)
 Invited talk at EUSIPCO2015 (2015)
 Member of Local Organisation Committee, LVA/ICA2010 (2010)
 IEEE Kansai Section Young Professionals Affinity Group (2014  Committee member; 2017  Treasurer)
 Member of Technical Committee on Engineering Acoustics, the Institute of Electronics, Information and Communication Engineers (IEICE), Japan (2017 )
 TPC member,
the Institute of Electronics, Information and Communication Engineers (IEICE) General Conference, Japan (2018)
 TPC member, the Institute of Electronics, Information and Communication Engineers (IEICE) Society Conference, Japan (2017)
 Committee member, Young Researcher Exchange Meeting, the Acoustical Society of Japan Kansai Branch (2013  2016)
 Deputy chair at the Spring/Autumn Meeting of the Acoustical Society of Japan
 Reviewer of journals including IEEE Trans. ASLP, IEEE SPL, ASJ, and IEICE
 Reviewer of conferences including ICASSP, EUSIPCO, and IWAENC
 Committee member, Student and Young Researchers Forum, the Acoustical Society of Japan (2011  2013)
Awards
 IWAENC 2018 Best Paper Award (2018)
 IEEE Signal Processing Society Japan Chapter Student Paper Award (2011)
 Japan Society for Industrial and Applied Mathematics Best Paper Award (2009)
 Itakura Prize Innovative Young Researcher Award, the Acoustical Society of Japan (2015)
 Awaya Prize Young Researcher Award, the Acoustical Society of Japan (2018)
 ASRU 2015 Best Paper Award Honorable Mention (2015)
 Best Student Presentation Award, the Acoustical Society of Japan (2011)
 Best Presentation Award, Young Researcher Exchange Meeting, the Acoustical Society of Japan Kansai Branch (2011)
 Senior Vice President's Award, Science and Core Technology Laboratory Group, NTT Corporation (2017)
 Vice President's Award, Communication Science Laboratories, NTT Corporation (2019)
 Vice President's Award, Communication Science Laboratories, NTT Corporation (2016)
 Vice President's Award, Communication Science Laboratories, NTT Corporation (2014)
Intern Supervision
 Christopher Schymura (RuhrUniversität Bochum, 2018.2  2018.3)
 Takashi Makino (Future University Hakodate, 2017.7  2017.8)
 Yuta Hashimoto (University of Toyama, 2017.7  2017.8)
 Juan Azcarreta (Polytechnic University of Catalonia, 2017.1  2017.8)
 Mahmoud Fakhry (University of Trento, 2015.11  2016.4)
 Kousuke Itakura (Kyoto University, 2015.8)
 Yu Teshima (Doshisha University, 2014.8)
 Ingrid Jafari (University of Western Australia, 2013)
Qualifications
 TOEIC Institutional Program (IP) 990 (2012.11)
 Eiken Grade 1 (2013.3)
Membership in Academic Societies
 Member of IEEE
 Member of the Acoustical Society of Japan
Publications
Journal Papers
 T. Higuchi, N. Ito, S. Araki, T. Yoshioka, M. Delcroix, and T. Nakatani, "Online MVDR Beamformer Based on Complex Gaussian Mixture Model with Spatial Prior for Noise Robust ASR," IEEE/ACM Trans. Audio, Speech, and Language Processing (ASLP), vol. 25, no. 4, pp. 780  793, Apr. 2017. [IEEE Xplore]
 M. Delcroix, T. Yoshioka, A. Ogawa, Y. Kubo, M. Fujimoto, N. Ito, K. Kinoshita, M. Espi, S. Araki, T. Hori, and T. Nakatani, "Strategies for Distant Speech Recognition in Reverberant Environments," EURASIP Journal on Advances in Signal Processing, DOI: 10.1186/s1363401502457, 2015.
[Springer]
 N. Ito, E. Vincent, T. Nakatani, N. Ono, S. Araki, and S. Sagayama, "Blind Suppression of Nonstationary Diffuse Acoustic Noise Based on Spatial Covariance Matrix Decomposition," Journal of Signal Processing Systems, vol. 79, no. 2, pp. 145  157, May 2015. [Springer]
(invited journal extension of a conference paper)
 N. Ito, S. Araki, K. Kinoshita, and T. Nakatani, "PermutationFree Clustering Method for Underdetermined Blind Source Separation Based on Source Location Information," IEICE (The Institute of Electronics, Information and Communication Engineers) Trans. Fundamentals of Electronics, Communications and Computer Sciences (Japanese Edition), vol. J97A, no. 4, pp. 234  246, Apr. 2014. [IEICE]
(in Japanese) (invited)
 N. Ito, H. Shimizu, N. Ono, and S. Sagayama, "Diffuse Noise Suppression Using CrystalShaped Microphone Arrays," IEEE Trans. Audio, Speech, and Language Processing (ASLP), vol. 19, no. 7, pp. 2101  2110, Sep. 2011. [IEEE Xplore]
(IEEE Signal Processing Society Japan Chapter Student Paper Award; Itakura Prize Innovative Young Researcher Award)
 N. Ono, N. Ito, Y. Izumi, and S. Sagayama, "On the Relationship between Separation Performance by Ideal TimeFrequency Masking and Sparseness of Sources," IEICE (The Institute of Electronics, Information and Communication Engineers) Trans. Fundamentals of Electronics, Communications and Computer Sciences (Japanese Edition), vol. J92A, no. 5, pp. 305  313, May 2009. [IEICE]
(in Japanese)
 N. Ito, T. Nara, and T. Sakurai, "Image Feature Extraction Based on Complex Moments," Japan Journal of Industrial and Applied Mathematics, vol. 18, no. 1, pp. 135  153, Apr. 2008. [CiNii]
(in Japanese) (Japan Society for Industrial and Applied Mathematics Best Paper Award)
Book Chapters
 N. Ito, S. Araki, and N. Tomohiro, "Recent Advances in Multichannel Source Separation and Denoising Based on Source Sparseness," in Audio Source Separation, S. Makino, Ed., Springer, pp. 279  300, 2018. [Springer]
 M. Delcroix, T. Yoshioka, N. Ito, A. Ogawa, K. Kinoshita, M. Fujimoto, T. Higuchi, S. Araki, and T. Nakatani, "Multichannel Speech Enhancement Approaches to DNNBased FarField Speech Recognition," in New Era for Robust Speech Recognition, S. Watanabe, M. Delcroix, F. Metze, and J.R. Hershey, Eds., Springer, pp. 21  49, 2017. [Springer]
 N. Ito, "What is Source Separation?", in Acousticpedia for Beginners, the Acoustical Society of Japan, Ed., Coronasha, pp. 40  43, 2017. (in Japanese) [Coronasha]
Tutorial Papers
 T. Nakatani, N. Ito, T. Higuchi, S. Araki, K. Kinoshita, "Multiple Microphone Speech Enhancement for Distant Speech Recognition," the journal of
the Institute of Noise Control Engineering of Japan (INCE/J), vol. 42, no. 1, pp. 16  19, Feb. 2018. (in Japanese) (invited)
 N. Ito, S. Araki, T. Nakatani, "Signal Enhancement in Any Environments," the Journal of the Acoustical Society of Japan, vol. 71, no. 3, pp. 136  142, Mar. 2015.(in Japanese) (invited)
International Conference Papers (Peer Reviewed)
 N. Ito and T. Nakatani, "FastMNMF: Joint Diagonalization Based Accelerated Algorithms for Multichannel Nonnegative Matrix Factorization," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 371  375, May 2019. [IEEE Xplore]
 N. Ito and T. Nakatani, "Multiplicative Updates and Joint Diagonalization Based Acceleration for UnderDetermined BSS Using a FullRank Spatial Covariance Model," Proc. IEEE Global Conf. Signal and Information Processing (GlobalSIP), pp. 231  235, Nov. 2018. [IEEE Xplore]
 N. Ito and T. Nakatani, "FastFCAAS: Joint Diagonalization Based Acceleration of FullRank Spatial Covariance Analysis for Separating Any Number of Sources," Proc. IEEE Int'l Workshop Acoustic Signal Enhancement (IWAENC), pp. 151  155, Sep. 2018. [IEEE Xplore] (IWAENC 2018 Best Paper Award)
 Y. Matsui, T. Nakatani, M. Delcroix, K. Kinoshita, N. Ito, S. Araki, and S. Makino, "Online Integration of DNNBased and Spatial ClusteringBased Mask Estimation for Robust MVDR Beamforming," Proc. IEEE Int'l Workshop Acoustic Signal Enhancement (IWAENC), pp. 71  75, Sep. 2018. [IEEE Xplore]
 N. Ito, S. Araki, and T. Nakatani, "FastFCA: Joint Diagonalization Based Acceleration of Audio Source Separation Using a FullRank Spatial Covariance Model," Proc. European Signal Processing Conf. (EUSIPCO), pp. 1681  1685, Sep. 2018. [EURASIP]
 N. Ito, C. Schymura, S. Araki, and T. Nakatani, "Noisy cGMM: Complex Gaussian Mixture Model with NonSparse Noise Model for Joint Source Separation and Denoising," Proc. European Signal Processing Conf. (EUSIPCO), pp. 1676  1680, Sep. 2018. [EURASIP]
 F.R. Stöter, A. Liutkus, and N. Ito, "The 2018 Signal Separation Evaluation Campaign," Proc. Int'l Conf. Latent Variable Analysis and Signal Separation (LVA/ICA), pp. 293  305, Jul. 2018. [Springer]
 N. Ito, T. Makino, S. Araki, and T. Nakatani, "MaximumLikelihood Online Speaker Diarization in Noisy Meetings Based on Categorical Mixture Model and Probabilistic Spatial Dictionary," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 546  550, Apr. 2018. [IEEE Xplore]
 J. Azcarreta, N. Ito, S. Araki, and T. Nakatani, "PermutationFree cGMM: Complex Gaussian Mixture Model with Inverse Wishart Mixture Model Based Spatial Prior for PermutationFree Source Separation and Source Counting," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 51  55, Apr. 2018. [IEEE Xplore]
 T. Higuchi, K. Kinoshita, N. Ito, S. Karita, and T. Nakatani, "FramebyFrame ClosedForm Update for MaskBased Adaptive MVDR Beamforming," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 531  535, Apr. 2018. [IEEE Xplore]
 N. Ito, S. Araki, and T. Nakatani, "DataDriven and Physical ModelBased Designs of Probabilistic Spatial Dictionary for Online Meeting Diarization and Adaptive Beamforming," Proc. European Signal Processing Conf. (EUSIPCO), pp. 1165  1169, Sep. 2017. [IEEE Xplore]
(invited)
 S. Araki, N. Ito, M. Delcroix, A. Ogawa, K. Kinoshita, T. Higuchi, T. Yoshioka, D. Tran, S. Karita, and T. Nakatani, "Online Meeting Recognition in Noisy Environments with TimeFrequency Mask Based MVDR Beamforming," Proc. Joint Workshop on Handsfree Speech Communication and Microphone Arrays (HSCMA), pp. 16  20, Mar. 2017. [IEEE Xplore]
 N. Ito, S. Araki, M. Delcroix, and T. Nakatani, "Probabilistic Spatial Dictionary Based Online Adaptive Beamforming for Meeting Recognition in Noisy and Reverberant Environments," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 681  685, Mar. 2017. [IEEE Xplore]
 T. Nakatani, N. Ito, T. Higuchi, S. Araki, and K. Kinoshita, "Integrating DNNBased and Spatial ClusteringBased Mask Estimation for Robust MVDR Beamforming," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 286  290, Mar. 2017. [IEEE Xplore]
 A. Liutkus, F.R. Stöter, Z. Rafii, D. Kitamura, B. Rivet, N. Ito, N. Ono, and J. Fontecave, "The 2016 Signal Separation Evaluation Campaign," Proc. Int'l Conf. Latent Variable Analysis and Signal Separation (LVA/ICA), pp. 323  332, Feb. 2017. [Springer]
 M. Fakhry, N. Ito, S. Araki, and T. Nakatani, "Modeling Audio Directional Statistics Using a Probabilistic Spatial Dictionary for Speaker Diarization in Real Meetings," Proc. IEEE Int'l Workshop Acoustic Signal Enhancement (IWAENC), DOI: 10.1109/IWAENC.2016.7602903, Sep. 2016. [IEEE Xplore]
 N. Ito, S. Araki, and T. Nakatani, "Complex Angular Central Gaussian Mixture Model for Directional Statistics in MaskBased Microphone Array Signal Processing," Proc. European Signal Processing Conf. (EUSIPCO), pp. 1153  1157, Sep. 2016. [IEEE Xplore]
 N. Ito, S. Araki, and T. Nakatani, "Modeling Audio Directional Statistics Using a Complex Bingham Mixture Model for Blind Source Extraction from Diffuse Noise," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 465  468, Mar. 2016. [IEEE Xplore]
 T. Higuchi, N. Ito, T. Yoshioka, and T. Nakatani, "Robust MVDR Beamforming Using TimeFrequency Masks for Online/Offline ASR in Noise," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 5210  5214, Mar. 2016. [IEEE Xplore]
 T. Yoshioka, N. Ito, M. Delcroix, A. Ogawa, K. Kinoshita, M. Fujimoto, C. Yu, W.J. Fabian, M. Espi, T. Higuchi, S. Araki, and T. Nakatani, "The NTT CHiME3 System: Advances in Speech Enhancement and Recognition for Mobile MultiMicrophone Devices," Proc. IEEE Workshop Automatic Speech Recognition and Understanding (ASRU), pp. 436  443, Dec. 2015. [IEEE Xplore]
(ASRU 2015 Best Paper Award Honorable Mention)
 N. Ito, S. Araki, and T. Nakatani, "PermutationFree Clustering of Relative Transfer Function Features for Blind Source Separation," Proc. European Signal Processing Conf. (EUSIPCO), pp. 409  413, Aug. 2015. [IEEE Xplore]
(invited)
 N. Ono, Z. Rafii, D. Kitamura, N. Ito, and A. Liutkus, "The 2015 Signal Separation Evaluation Campaign," Proc. Int'l Conf. Latent Variable Analysis and Signal Separation (LVA/ICA), pp. 387  395, Aug. 2015. [Springer]
 M. Delcroix, T. Yoshioka, A. Ogawa, Y. Kubo, M. Fujimoto, N. Ito, K. Kinoshita, M. Espi, S. Araki, T. Hori, and T. Nakatani, "Defeating Reverberation: Advanced Dereverberation and Recognition Techniques for HandsFree Speech Recognition," Proc. IEEE Global Conf. Signal and Information Processing (GlobalSIP), pp. 522  526, Dec. 2014. [IEEE Xplore] (invited)
 N. Ito, S. Araki, T. Yoshioka, and T. Nakatani, "Relaxed Disjointness Based Clustering for Joint Blind Source Separation and Dereverberation," Proc. IEEE Int'l Workshop Acoustic Signal Enhancement (IWAENC), pp. 268  272, Sep. 2014. [IEEE Xplore]
 M. Delcroix, T. Yoshioka, A. Ogawa, Y. Kubo, M. Fujimoto, N. Ito, K. Kinoshita, M. Espi, T. Hori, T. Nakatani, and A. Nakamura, "Linear PredictionBased Dereverberation with Advanced Speech Enhancement and Recognition Technologies for the REVERB Challenge," Proc. REVERB Workshop, May 2014. [REVERB Workshop]
 N. Ito, S. Araki, and T. Nakatani, "Probabilistic Integration of Diffuse Noise Suppression and Dereverberation," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 5167  5171, May 2014. [IEEE Xplore]
 N. Ono, Z. Koldovský, S. Miyabe, and N. Ito, "The 2013 Signal Separation Evaluation Campaign," Proc. IEEE Int'l Workshop Machine Learning for Signal Processing (MLSP), DOI: 10.1109/MLSP.2013.6661988, Sep. 2013. [IEEE Xplore]
 N. Ito, E. Vincent, N. Ono, and S. Sagayama, "General Algorithms for Estimating Spectrogram and Transfer Functions of Target Signal for Blind Suppression of Diffuse Noise," Proc. IEEE Int'l Workshop Machine Learning for Signal Processing (MLSP), DOI: 10.1109/MLSP.2013.6661984, Sep. 2013. [IEEE Xplore] (invited to journal extension)
 I. Jafari, N. Ito, M. Souden, S. Araki, and T. Nakatani, "Source Number Estimation Based on Clustering of Speech Activity Sequences for Microphone Array Processing," Proc. IEEE Int'l Workshop Machine Learning for Signal Processing (MLSP), DOI: 10.1109/MLSP.2013.6661990, Sep. 2013. [IEEE Xplore]
 N. Ito, S. Araki, and T. Nakatani, "PermutationFree Convolutive Blind Source Separation via FullBand Clustering Based on FrequencyIndependent Source Presence Priors," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 3238  3242, May 2013. [IEEE Xplore]
 N. Ito, E. Vincent, N. Ono, R. Gribonval, and S. Sagayama, "CrystalMUSIC: Accurate Localization of Multiple Sources in Diffuse Noise Environments Using CrystalShaped Microphone Arrays," Proc. Int'l Conf. Latent Variable Analysis and Signal Separation (LVA/ICA), pp. 81  88, Sep. 2010. [Springer]
 N. Ito, N. Ono, E. Vincent, and S. Sagayama, "Designing the Wiener PostFilter for Diffuse Noise Suppression Using Imaginary Parts of InterChannel CrossSpectra," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 2818  2821, Mar. 2010. [IEEE Xplore]
 N. Ono, H. Kohno, N. Ito, and S. Sagayama, "Blind Alignment of Asynchronously Recorded Signals for Distributed Microphone Array," Proc. IEEE Workshop Applications of Signal Processing to Audio and Acoustics (WASPAA), pp. 161  164, Oct. 2009. [IEEE Xplore]
 Y. Kamamoto, N. Harada, T. Moriya, N. Ito, N. Ono, T. Nishimoto, and S. Sagayama, "An Efficient Lossless Compression of Multichannel TimeSeries Signals by MPEG4 ALS," Proc. IEEE Int'l Symposium Consumer Electronics (ISCE), pp. 159  163, May 2009. [IEEE Xplore]
 N. Ono, N. Ito, and S. Sagayama, "Five Classes of Crystal Arrays for Blind Decorrelation of Diffuse Noise," Proc. IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM), pp. 151  154, Jul. 2008. [IEEE Xplore]
 N. Ito, N. Ono, and S. Sagayama, "A Blind Noise Decorrelation Approach with Crystal Arrays on Designing PostFilters for Diffuse Noise Suppression," Proc. IEEE Int'l Conf. Acoustics, Speech, and Signal Processing (ICASSP), pp. 317  320, Apr. 2008. [IEEE Xplore]
 T. Nara, N. Ito, T. Takamatsu, and T. Sakurai, "Direct Computation of Harmonic Moments for Tomographic Reconstruction," Journal of Physics: Conference Series, vol. 73, DOI: 10.1088/17426596/73/1/012017, 2007. [IOPSCIENCE]
Preprints
 N. Ito and T. Nakatani, "FastFCAAS: Joint Diagonalization Based Acceleration of FullRank Spatial Covariance Analysis for Separating Any Number of Sources," arXiv,
arXiv:1805.09498, May 2018.
 N. Ito, S. Araki, and T. Nakatani, "FastFCA: A Joint Diagonalization Based Fast Algorithm for Audio Source Separation Using a FullRank Spatial Covariance Model," arXiv, arXiv:1805.06572, May 2018.
 F.R. Stöter, A. Liutkus, and N. Ito, "The 2018 Signal Separation Evaluation Campaign," arXiv, arXiv:1804.06267, Apr. 2018.
 N. Ito, E. Vincent, N. Ono, and S. Sagayama, "Robust Estimation of DirectionsofArrival in Diffuse Noise Based on MatrixSpace Sparsity," Research Report, INRIA, RR8120, hal00746271, Oct. 2012.
 T. Nara, N. Ito, S. Ando, T. Takamatsu, and T. Sakurai, "Direct Computation of Harmonic Moments for Tomographic Reconstruction," Mathematical Engineering Technical Reports, the University of Tokyo, METR 200658, Nov. 2006.
Domestic Conference Papers (Not Peer Reviewed)
 N. Ito, S. Araki, and T. Nakatani, "FastFCA: Fast Algorithm for Audio Source Separation Using TimeVarying Complex Gaussian Distribution Based on Joint Diagonalization of Spatial Covariance Matrices," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 427  430, 2018. (in Japanese)
 N. Ito, S. Araki, M. Delcroix, and T. Nakatani, "Speech Enhancement for Meeting Speech Recognition Based on Online Speaker Diarization and Adaptive Beamforming Using Probabilistic Spatial Dictionary," Proc. Autumn Meeting of the Acoustical Society of Japan (ASJ), 2017. (in Japanese)
 N. Ito, S. Araki, and T. Nakatani, "Complex Angular Central Gaussian Mixture Model for Directional Statistics Based Blind Source Separation," Proc. Autumn Meeting of the Acoustical Society of Japan (ASJ), 2017. (in Japanese) (Awaya Prize Young Researcher Award)
 S. Araki, K. Kinoshita, N. Ito, A. Ogawa, M. Delcroix, T. Higuchi, T. Yoshioka, D. Tran, and T. Nakatani, "Conversation Speech Recognition in Noisy Environments," Proc. Autumn Meeting of the Acoustical Society of Japan (ASJ), pp. 1265  1268, 2016. (in Japanese)(invited)
 N. Ito, S. Araki, M. Fakhry, and T. Nakatani, "Multiple Speaker Diarization Based on Modeling Directional Statistics Using Statistical Spatial Dictionary," Proc. Autumn Meeting of the Acoustical Society of Japan (ASJ), pp. 321  324, 2016. (in Japanese)
 N. Minematsu, Y. Akita, T. Asami, N. Ito, T. Ochiai, T. Koriyama, D. Saito, S. Shiota, T. Shinozaki, M. Suzuki, S. Takagi, N. Tawara, K. Hashimoto, T. Higuchi, and T. Fukuda, "Attendance Report of International Conference ICASSP2016," the Special Interest Group Technical Reports of Information Processing Society of Japan (IPSJ), vol. 2016SLP112, no. 5, pp. 1  6, Jul. 2016. (in Japanese)
 N. Ito, S. Araki, and T. Nakatani, "Complex Bingham Mixture Models for Directional Statistics Modeling and Blind Diffuse Noise Reduction," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 629  630, 2016. (in Japanese)
 T. Higuchi, N. Ito, T. Yoshioka, and T. Nakatani, "Online MVDR Beamforming Based on TimeFrequency Masking," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 559  560, 2016. (in Japanese)
 T. Nakatani, N. Ito, T. Higuchi, S. Araki, T. Yoshioka, M. Fujimoto, and K. Kinoshita, "NTT CHiME3 Speech Recognition System: NoiseRobust Frontend," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 57  60, 2016. (in Japanese)
 T. Yoshioka, M. Delcroix, A. Ogawa, C. Yu, N. Ito, K. Kinoshita, M. Fujimoto, W. Fabian, M. Espi, T. Higuchi, S. Araki, and T. Nakatani, "NTT CHiME3 Speech Recognition System: System Overview and BackEnd Techniques," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 55  56, 2016. (in Japanese)
 N. Ito, S. Araki, and T. Nakatani, "Multichannel Noise Suppression Based on PermutationFree Clustering," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 587  588, 2015. (in Japanese)
 N. Ito, S. Araki, and T. Nakatani, "Probabilistic Model Integration of ClusteringBased Source Separation and Linear PredictionBased Dereverberation," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 547  548, 2015. (in Japanese)
 N. Ito, S. Araki, and T. Nakatani, "Joint Blind Source Separation and Counting for Reverberant Underdetermined Mixtures Based on Source Location and Activation," Proc. Autumn Meeting of the Acoustical Society of Japan (ASJ), pp. 521  522, 2014. (in Japanese)
 M. Delcroix, K. Kinoshita, T. Yoshioka, A. Ogawa, Y. Kubo, M. Fujimoto, N. Ito, M. Espi, T. Hori, T. Nakatani, and A. Nakamura, "Speech Enhancement and Recognition for Reverberant Speech: Overview of the NTT REVERB Challenge System," the Special Interest Group Technical Reports of Information Processing Society of Japan (IPSJ), vol. 2014SLP102, no. 5, pp. 1  4, Jul. 2014. (in Japanese)
 N. Ito, S. Araki, and T. Nakatani, "Joint Blind Suppression of Diffuse Noise and Reverberation Based on Probabilistic Model Integration," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 667  668, 2014. (in Japanese)
 N. Ito, I. Jafari, S. Araki, and T. Nakatani, "Source Number Estimation under Reverberant and Underdetermined Conditions Based on Clustering of Source Activity Sequences," Technical Report of the Institute of Electronics, Information and Communication Engineers (IEICE), vol. 113, no. 242, pp. 17  21, Oct. 2013. (in Japanese)
 N. Ito, S. Araki, and T. Nakatani, "PermutationFree ClusteringBased Source Separation Based on TimeVarying Mixture Weights," Technical Report of the Institute of Electronics, Information and Communication Engineers (IEICE), vol. 113, no. 28, pp. 7  12, May 2013. (in Japanese)
 N. Ito, E. Vincent, N. Ono, R. Gribonval, and S. Sagayama, "Diffuse Noise Robust Multiple Source Localization Based on Matrix Completion via Trace Norm Minimization," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 665  666, 2011. (in Japanese) (Best Student Presentation Award)
 T. Ono, N. Ito, S. Miyabe, N. Ono, and S. Sagayama, "Blind Source Separation with Distributed Microphone Arrays and Investigation of Performance Gain Using PostFilter," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 655  656, 2011. (in Japanese)
 T. Ono, N. Ito, S. Miyabe, N. Ono, and S. Sagayama, "Blind Source Separation with Distributed Microphone Pairs and Investigation of Performance Gain Using PostFilter," Technical Report of the Institute of Electronics, Information and Communication Engineers (IEICE), vol. 110, no. 331, pp. 25  30, Dec. 2010. (in Japanese)
 N. Ito, Y. Kitano, N. Ono, and S. Sagayama, "Instrument Separation in Reverberant Environments Using Crystal Microphone Arrays," the Special Interest Group Technical Reports of Information Processing Society of Japan (IPSJ), vol. 2009MUS82, no. 3, pp. 1  6, Dec. 2009. (in Japanese)
 N. Ito, N. Ono, and S. Sagayama, "Diffuse Noise Suppression Based on the Imaginary Parts of the InterChannel CrossSpectra with a SmallSized Microphone Array," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 705  706, 2009. (in Japanese)
 H. Kohno, N. Ito, N. Ono, and S. Sagayama, "Blind Alignment of Received Signals to Localize Sources and Microphones," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 703  704, 2009. (in Japanese)
 N. Ito, N. Ono, and S. Sagayama, "Investigation of RealEnvironmental Noise Suppression with a Crystal Array," Proc. Autumn Meeting of the Acoustical Society of Japan (ASJ), pp. 677  678, 2008. (in Japanese)
 N. Ito, N. Ono, and S. Sagayama, "Diffuse Noise Suppression by CrystalArrayBased PostFilter Design," Technical Report of the Institute of Electronics, Information and Communication Engineers (IEICE), vol. 108, no. 68, pp. 43  46, May 2008. (in Japanese)
 N. Ito, N. Ono, and S. Sagayama, "Diffuse Noise Suppression Based on PostFiltering Using Crystal Arrays," Proc. Spring Meeting of the Acoustical Society of Japan (ASJ), pp. 695  696, 2008. (in Japanese)
 S. Araki, N. Ito, H. Sawada, N. Ono, S. Makino, and S. Sagayama, "Initial Value Estimation for Frequency Domain ICA from Limited Data," Proc. the Institute of Electronics, Information and Communication Engineers (IEICE) General Conference, p. 208, Mar. 2008. (in Japanese)
 N. Ono, Y. Izumi, N. Ito, and S. Sagayama, "Source Separation by TimeVariant Filters Based on Stochastic Models," Technical Report of the Institute of Electronics, Information and Communication Engineers (IEICE), vol. 107, no.240, pp. 25  30, Sep. 2007. (in Japanese) (invited)
 N. Ono, H. Kohno, H. Shimizu, N. Ito, and S. Sagayama, "A Grouptheoretical Consideration on Array Arrangements to Orthogonalize Isotropic Noise Field," Proc. Autumn Meeting of the Acoustical Society of Japan (ASJ), pp. 621  622, 2007. (in Japanese)
 N. Ito, N. Ono, and S. Sagayama, "A Nonlinear Beamformer in the Isotropic Noise Field Using Crystal Arrays," Proc. Autumn Meeting of the Acoustical Society of Japan (ASJ), pp. 619  620, 2007. (in Japanese)
Conference Presentations (No Proceedings)
 N. Ito, S. Araki, and T. Nakatani, "A New Application of Joint Diagonalization Based on the Generalized Eigenvalue Problem: Computation Reduction of Source Separation," Meeting of the Union of Research Activity Groups,
Japan Society for Industrial and Applied Mathematics,
Mar. 2018. (in Japanese)
 N. Ito, T. Nara, and T. Sakurai, "On Complex Moments of Images and their Projections," Meeting of the Union of Research Activity Groups,
Japan Society for Industrial and Applied Mathematics, Mar. 2007. (in Japanese)
 T. Nara, N. Ito, S. Ando, T. Takamatsu, and T. Sakurai, "Direct Computation of Harmonic Moments from Projections," The 6th Symposium of Mathematical Aspects of Image Processing and Computer Vision, Nov. 2006. (invited)
Theses
 "Robust Microphone Array Signal Processing against Diffuse Noise,"
Ph.D. Dissertation, the University of Tokyo, Japan, Mar. 2012.

"Microphone Array Signal Processing for Diffuse Noise Suppression,"
Master's Thesis, the University of Tokyo, Japan, Mar. 2009.

"Study on Complex Moments of Images and their Projections,"
Bachelor's Thesis, the University of Tokyo, Japan, Mar. 2007. (in Japanese)