Hari Vishnu

Research Fellow

Hari Vishnu

Hari Vishnu obtained his Ph.D degree in 2013 from the Nanyang Technological University (NTU), Singapore, in Computer Engineering. He did his B.Tech in Electronics and Electrical Engineering from National Institute of Technology, Calicut, in 2008.

He joined ARL in 2013. His current research interests at ARL are in machine learning for underwater applications, bio-acoustics and signal processing in impulsive noise. Applications span fields ranging from shallow tropical waters infested with snapping shrimp noise, to the depths of the ocean, to the Arctic ice sheets where glacier melt noise dominates the soundscape. His Ph.D research involved the development of improved algorithms for underwater signal processing. These included detection & localization, acoustic propagation modeling and vector sensor processing, and developing robust methods in impulsive noise.

Hari is currently also a Visiting Scholar at the Scripps Institution of Oceanography, working on the acoustics of melting ice.

He is the Chief Editor on the OES Science outreach magazine Earthzine. In 2019, he was awarded the IEEE Oceanic Engineering society's YP-BOOST award which aims to encourage young professionals to participate in the leadership of the society by attending OES meetings, being involved in the diverse committees, and helping with different aspects of the IEEE OCEANS conferences.

He has been the chair of the IEEE OES, Singapore chapter for 2018-2020, and also the Secretary of the Singapore AUV Challenge since 2016. Through 2015-2017, he was involved with IEEE OES in several roles such as Secretary, Webmaster and Executive committee member of the Singapore chapter.

Hari has been involved with student technical activities since his Bachelors days, where he served on the IEEE Student Branch at NIT Calicut as Public relations officer and Secretary. During this period, he was instrumental in helping give birth to robotics initiatives at NITC, and also in conducting the popular FOSS open source software meet at NITC.

Apart from research, he enjoys reading, gardening, listening to music and playing the flute. He is also passionate about anime, movies and TV series.

Email: tmshv (at) nus.edu.sg

Find me at Google scholar.

Find Earthzine here.

Some of my code is public at my Github repo .

Research Interests



  1. L. J. Wong, B. Kalyan, M. Chitre and V. N. Hari, "Acoustic Assessment of Polymetallic Nodule Abundance Using Sidescan Sonar and Altimeter," IEEE Journal of Oceanic Engineering, 2020, DOI: 10.1109/JOE.2020.2967108 [http]
  2. C. Chi, V. Hari, T. B. Koay and Mandar Chitre, "Utilizing Orthogonal Coprime Signals for Improving Broadband Acoustic Doppler Current Profilers," IEEE Journal of Oceanic Engineering, 2019, DOI: 10.1109/JOE.2019.2925922 [http] [.pdf]
  3. M Chitre, J Tian and V. Hari, "On Ambiguity Function Shaping for Broadband Constant-Modulus Signals," Signal Processing, 2019, DOI: 10.1016/j.sigpro.2019.07.017 [http] [.pdf]
  4. C. Chi, V. Hari, T. B. Koay and Mandar Chitre, "Robust Resolution of Velocity Ambiguity for Multifrequency Pulse-to-Pulse Coherent Doppler Sonars," IEEE Journal of Oceanic Engineering, 2019, DOI: 10.1109/JOE.2019.2925919 [http] [.pdf]
  5. S. L. Rigel Goh, V. Hari and Ngan Kee Ng, "The sounds of fighting: contests between violet vinegar crabs, Episesarma versicolor (Decapoda: Brachyura: Sesarmidae) are resolved through acoustic communication," Journal of Crustacean Biology, 2019, DOI: 10.1093/jcbiol/ruz023
  6. V. N. Hari, B. Kalyan, M. Chitre and V. Ganesan, "Spatial modeling of deep-sea ferromanganese nodules with limited data using neural networks", IEEE Journal of Oceanic Engineering, vol. 43, No. 4, Oct 2018, DOI: 10.1109/JOE.2017.2752757 [http] [.pdf] © IEEE 2017
  7. A. Mahmood, M. Chitre, and V. Hari, "Locally-Optimal Inspired Detection in Snapping Shrimp Noise," IEEE Journal of Oceanic Engineering, 2017, vol. 24, No. 4, Oct 2017, DOI: 10.1109/JOE.2017.2731058 [http] [.pdf] © IEEE 2017
  8. V. N. Hari and M. Chitre, “Robust estimation of modulation frequency in impulsive acoustic data,” IEEE Transactions on Aerospace and Electronic Systems, Mar 2017, DOI: 10.1109/TAES.2017.2677621 [http][.pdf] © IEEE 2017 . Code is available at my Github repo.
  9. V. N. Hari, G. V. Anand and A. B. Premkumar, “Narrowband signal detection techniques in shallow ocean by acoustic vector sensor array”, Digital Signal Processing, vol. 23 pp. 1645-1661, June 2013, [.pdf][http]©Elsevier
  10. V. N. Hari, A. B. Premkumar, and X. Zhong, “A Decoupled Approach for Near-Field Source Localization Using a Single Acoustic Vector Sensor”, Circuits, Systems, and Signal Processing, vol. 32, no. 2, pp. 843–859, Oct. 2012.[http] [.pdf] ©Springer
  11. V. N. Hari, G. V. Anand, A. B. Premkumar, and A. S. Madhukumar, “Design and performance analysis of a signal detector based on suprathreshold stochastic resonance”, Signal Processing, vol. 92, no. 7, pp. 1745–1757, Jul. 2012. [http] [.pdf] ©Elsevier .

Invited conference talks

  1. A. Mahmood, V. N. Hari and M. Chitre, "Model Based Signal Detection in Snapping Shrimp Noise", Underwater Communications and Network (UComms 2016), Lerici, Italy, September 2016 [http] [.pdf] <
  2. G. V. Anand, V. N. Hari and Z. Madadi, "Signal detection in non-Gaussian noise", SYMPOL 2011, Kochi, 2011

Conferences and posters

  1. Hari Vishnu, Mandar Chitre, O. Glowacki, M. Moskalik, D. Stokes, G. Deane, “Vertical line array measurements of the sound radiated by melting glaciers in Hornsund Fjord “, Acoustic Society of America Fall Meeting, 2020, Chicago (Accepted)
  2. Grant B. Deane, Oskar Glowacki, Dale M. Stokes, Mateusz Moskalik, Mandar Chitre and Hari Vishnu, "Measuring tidewater glacier melt rates with underwater noise", Ocean Sciences meeting, Feb 2020 [http]
  3. L. J. Wong, V. Pallayil, P. Muthuvel, K. Amudha, B. Kalyan, V. Hari, M. A. Atmanand and M. Chitre, "Acoustic Backscattering Properties of Polymetallic Nodules from the Indian Ocean Basin: Results from a Laboratory Measurement", IEEE Underwater Technology 2019, Kaouhsiong, Apr 2019 [http] [.pdf]
  4. V. Hari, V. Robert, B. Kalyan and M. Chitre, "A semi-supervised learning approach to polymetallic nodule parameter modeling", IEEE Oceans 2018, Charleston, Oct 2018 [http] [.pdf]
  5. C. Chi, V. Hari and M. Chitre, "A Metric for Selecting Waveforms of Multi-User Wideband Active Sonars", IEEE Oceans 2018, Charleston, Oct 2018 [http] [.pdf]
  6. C. Chi, V. Hari and T. B. Koay, "Resolving Velocity Ambiguity Based on Robust Chinese Remainder Theorem for Multi-Frequency Pulse-to-Pulse Coherent Doppler Sonar", IEEE Oceans 2018, Charleston, Oct 2018 [http]
  7. B. Kalyan, R. Mishra, V. Hari and M. Chitre, "An Information Theoretic Approach to Polymetallic Nodule Exploration using AUVs", (Accepted) Underwater Mining Conference 2018, Bergen, Norway.
  8. C. Chi, V. Hari and T. B. Koay, "Improving broadband acoustic Doppler current profiler with orthogonal coprime pulse pairs and robust chinese remainder theorem", IEEE Oceans 2018, Kobe, May 2018 [http] [.pdf]
  9. S. Ahmed, V. Hari and M. Chitre, "Monostatic sonar performance using pulse compression waveforms", IEEE Oceans 2018, Kobe, May 2018 [http] [.pdf]
  10. V. Hari , B. Kalyan and M. Chitre, "Spatial modeling and uncertainty characterization of polymetallic nodules in the Clarion-Clipperton zone", IEEE Oceans 2017, Anchorage, Sep 2017 [http] [.pdf]
  11. V. Kalaiarasu, V. Hari, A. Mahmood and M. Chitre, "Predicting underwater acoustic network variability using machine learning techniques", IEEE Oceans 2017, Anchorage, Sep 2017 [http] [.pdf]
  12. A. Mahmood, M. Chitre and V. Hari, "Spatial ambient noise inversion using a single hydrophone", IEEE Oceans 2017, Anchorage, Sep 2017 [http] [.pdf]
  13. B. Kalyan, V. Ganesan, M. Chitre and V. Hari," Optimal point planning for abundance estimation of polymetallic nodules", IEEE Oceans 2017, Anchorage, Sep 2017 [http] [.pdf]
  14. Wong Liang Jie, B. Kalyan, M. Chitre and V. N. Hari, "Polymetallic Nodules Abundance Estimation using Sidescan Sonar: A Quantitative Approach using Artificial Neural Network", IEEE Oceans 2017, Aberdeen, Scotland, Jun 2017 [http] [.pdf]
  15. M. Hoffman-Kuhnt, Abel Ho, V. N. Hari, M. Chitre and E. Matrai , Alice Tse, "Buzz that Rod ! Acoustic Analysis and patterns of the echolocation signals of a blindfolded bottlenose dolphin performing a horizontal and vertical angular resolution task", Proceedings of 2015 Society for Marine Mammalogy Biennial Conference, San Francisco, Dec 13-18 [.pdf]
  16. K. C. Unnikrishnan and V. N. Hari, "A vector sensing scheme for underwater acoustics based on particle velocity measurements", IEEE Oceans 2015, Washington DC, USA, Oct 2015 [http] [.pdf]
  17. X. Zhong, V. N. Hari, X. Shen, H. Wang, W. Wang, "Particle filtering for channel parameter tracking in a noisy shallow ocean environment using a vertical array", Asia-Pacific Conference on Synthetic Aperture Radar 2015, Singapore, Sep 2015 [http]
  18. V. N. Hari, M. Chitre, Y. M. Too and V. Pallayil, “Robust passive diver detection in shallow ocean”, IEEE Oceans 2015, Genova, Italy [http] [.pdf]
  19. V. N. Hari, M. Chitre, "Robust signal processing in impulsive noise for Sonar", DSO Tech-know exhibition, Singapore, Jul 2014
  20. V. N. Hari, X. Zhong, A. B. Premkumar, "Near-field/far-field source localization in ocean with an acoustic vector sensor array using polynomial rooting", Proc. SYMPOL 2013, Kochi, India, Oct 2013 [.pdf] [http]
  21. V. N. Hari, G. V. Anand, and A. B. Premkumar, “Narrowband detection in ocean with impulsive noise using an acoustic vector sensor array” , in 20th European Signal Processing Conference (EUSIPCO 2012), 2012, pp. 1334–1339. [.pdf] [http]
  22. X. Zhong, V. N. Hari and A. B. Premkumar, " An Optimal Importance Sampling based Particle Filtering for Channel Parameter Estimation in Shallow Ocean", Proc. IEEE Global Conference on Consumer Electronics 2012, Tokyo, Oct 2012. [http]
  23. V. N. Hari, G. V. Anand, A. B. Premkumar, and A. S. Madhukumar, “Underwater signal detection in partially known ocean using short acoustic vector sensor array”, in OCEANS 2011 IEEE - Spain, 2011, no. 65, pp. 1–9. [.pdf] [http]
  24. X. Zhong, V. N. Hari, A. B. Premkumar, and A. S. Madhukumar, “Particle filtering with enhanced likelihood model for underwater acoustic source DOA tracking”, in OCEANS 2011 IEEE - Spain, 2011, pp. 1–6. [http]
  25. V. N. Hari, G. V. Anand, and A. B. Premkumar, “Preprocessor based on suprathreshold stochastic resonance for improved bearing estimation in shallow ocean”, in OCEANS 2009, MTS, 2009, no. 65, pp. 1–8. [.pdf] [http]©IEEE 2009
  26. V. N. Hari, G.V. Anand , A. B. Premkumar, "Optimal suprathreshold stochastic resonance based nonlinear detector", Proc. 17th European Signal Processing conference (EUSIPCO 2009), Glasgow, 2009, pp. 2062 – 2066. [.pdf]


  1. V. N. Hari, "Improved techniques for detection and localization of underwater acoustic sources using acoustic vector sensors", Ph.D thesis, School of Computer Engineering, Nanyang Technological University, Singapore, 2013

Selected articles published on Earthzine

  1. Hari Vishnu, "AUV-related research articles in April issue of IEEE JOE", July, 2020
  2. Hari Vishnu, "UN Decade of Ocean Science for Sustainable development – Outreach (Part 1/2)", June, 2020
  3. Hari Vishnu, "Climate Science for the public – The IPCC report on Ocean and Cryosphere", March, 2020
  4. Liang Jie, Wong, and Hari Vishnu, "OCEANS ’19 Marseille: Analysis of the number of papers mentioning machine learning", February 2020
  5. Hari Vishnu, (Editorial) "Earthzine announces Plastics theme for first quarter of 2020", January 2020
  6. Hari Vishnu and Rene Garello, "Data. To store or not to store, that is the question", October 2019
  7. Hari Vishnu, "Arctic Research at Oceans 2019 - A summary", September 2019
  8. Hari Vishnu, (Editorial) "Earthzine resumes operations", August 2019