Ambient Noise Imaging (ANI)

The principle underlying ANI makes use of the ensonification provided by the ambient noise field to create pictorial images of underwater objects. ANI is well suited for the warm shallow waters of south east Asia, where snapping shrimp serve as an excellent source of acoustic illumination. Snapping shrimp are also found in many other warm shallow water areas around the world.

The ARL has developed a class of new algorithms including the one based on the acoustic daylight idea to form images out of the ambient noise data. ARL has also built a system called Remotely Operated Mobile Ambient Noise Imaging System (ROMANIS), an ambient noise imaging underwater acoustic camera. The system was built several years ago and functionally tested. It is now being upgraded for a deployment later this year.

ROMANIS

ROMANIS is a digital broad band ANI camera which is able to form high resolution images over 25-85 kHz acoustic frequency band. The ARL has already built the camera and it has undergone so far two successful functional trials in Singapore waters. Some of the highlights of the system are:

A fully populated but sparsely sampled 1.5m diameter circular array comprising of 504 hydrophone elements
Broadband system covering 25-85 kHz
Hierarchical and modular design
Synchronous sampling and the data streamed at the rate of 1.6 Gbps
No potted or oil-filled sensors; a neoprene acoustic window
Gas filled with 0.5 bar of Helium for better thermal conduction

Preliminary Results

ROMANIS has been deployed at Raffles Anchorage in Singapore twice. The first deployment was to check the system operations in a real seawater environment while the second deployment was aimed at the functional testing of the system towards beamforming and forming images of certain stationary targets. The system functionality has been established and images of a stationary target at about 70 m away from ROMANIS have been formed.

The reflective target panels were built from a 1 m x 1 m aluminum sheet with 6 mm neoprene closed cell sponge on one side and 15 mm Klegecell on the other side. The panels were then slotted into a target frame to create different shapes. Below is the target frame used for the trials.

The second deployment of ROMANIS attempted to form images of right rotated "L" and following are the images obtained. The target shape is also shown for reference.

Related Publications

[1]	J. R. Potter, “Shallow Water Ambient Noise Imaging Camera Developed at the ARL,” in Defence R&D Seminar, Singapore, May 23 2006. Keynote paper.
[2]	J. R. Potter, V. Pallayil, M. A. Chitre, T. B. Koay, S. P. Tan, E. T. Tan, and P. D. Deshpande, “Shallow Water Ambient Noise Imaging Camera Developed at the ARL,” in Defence Research and Development conference, NTU, Singapore 2006, Singapore, May 23 2006.
[3]	V. Pallayil, M. A. Chitre, E. T. Tan, J. R. Potter, T. B. Koay, S. B. Ruiz, and S. P. Tan, “Ambient noise imaging - First deployments of ROMANIS and preliminary data analysis,” in OCEANS 2003 MTS/IEEE: CELEBRATING THE PAST...TEAMING TOWARD THE FUTURE, pp. 882-888, September 2003. MTS/IEEE Conference on Celebrating the Past - Teaming Toward the Future, San Diego, CA, September 22-26, 2003. [ .pdf ]
[4]	T. B. Koay, E. T. Tan, M. Chitre, and J. Potter, “Estimating the spatial and temporal distribution of snapping shrimp using a portable, broadband 3-dimensional acoustic array,” in OCEANS 2003. Proceedings, vol. 5, pp. 2706-2713, September 2003. [ DOI \| .pdf ]
[5]	J. R. Potter, “Ambient Noise Imaging techniques and potential in warm shallow water,” in Proceedings of the ASW Asia workshop, Singapore, 2003. [ .pdf ]
[6]	J. R. Potter, “Detection, classification and tracking of marine mammals using passive, active and ambient noise techniques,” in European Cetacean Society conference, Gran Canaria, Spain, 2003.
[7]	J. R. Potter and L. Malod, “Expanding uses of ambient noise for imaging, detection and communication,” in Acoustical Society of America meeting, Cancun, Mexico, 2003.
[8]	T. B. Koay, E. T. Tan, and J. Potter, “A portable, self-contained, 5MSa/s data acquisition system for broadband, high frequency acoustic beamforming,” in OCEANS '02 MTS/IEEE, vol. 1, pp. 369-378 vol.1, October 2002. [ DOI \| .pdf ]
[9]	C. K. Lim and J. R. Potter, “Ambient Noise Imaging; enhanced spatial correlation algorithms and a way to combine independent images for improved stability and false alarm rate,” in Proceedings of Underwater Technology 2002, Tokyo, Japan, pp. 196-201, 2002. [ .pdf ]
[10]	E. Delory, M. André, and J. R. Potter, “An ambient noise imaging sonar to detect non-vocalising sperm whales,” in Proceedings of the European Cetacean Society Meeting, 2002. [ .pdf ]
[11]	J. R. Potter, V. Pallayil, and L. Malod, “Coherent Ambient Noise Imaging in shallow water,” in NUWC ASW workshop, Rhode Island, 2002.
[12]	H. Zhang, T. B. Koay, V. Pallayil, Y. Zhang, and J. R. Potter, “Fibre channel storage area network design for an acoustic camera system with 1.6 gbits/s bandwidth,” in IEEE REGION 10 International conference on electrical and electronic technology (D. Tien and Y. Liang, eds.), vol. 1, 2, pp. 143-148, August 2001. IEEE Region 10 International Conference on Electrical and Electronic Technology, SINGAPORE, SINGAPORE, August 19-22, 2001. [ .pdf ]
[13]	M. J. Buckingham, J. R. Potter, and C. Epifanio, “Acoustic imaging,” Pour La Science, French Edition of Scientific American, vol. 32, pp. 54-57, 2001.
[14]	J. R. Potter and T. B. Koay, “Do snapping shrimp chorus in time or cluster in space? Temporal-spatial studies of high-frequency ambient noise in Singapore waters,” in European Conference on Underwater Acoustics 2000, Lyons, France, July 2000. [ .pdf ]
[15]	M. A. Chitre, “Optimisation of ambient noise imaging through simulation and modelling,” Master's thesis, National University of Singapore, 2000.
[16]	J. R. Potter and M. A. Chitre, “Ambient noise imaging in warm shallow seas; second-order moment and model-based imaging algorithms,” Journal Of The Acoustical Society Of America, vol. 106, pp. 3201-3210, December 1999. [ .pdf ]
[17]	C. L. Epifanio, J. R. Potter, G. B. Deane, M. L. Readhead, and M. J. Buckingham, “Imaging in the ocean with ambient noise: the ORB experiments,” Journal Of The Acoustical Society Of America, vol. 106, pp. 3211-3225, December 1999. [ .pdf ]
[18]	V. Pallayil, P. D. Deshpande, S. Badiu, S. Constantin, B. Lu, and J. R. Potter, “A 1.6 Gigabit/second, 25-85 kHz Acoustic Imaging Array- Novel Mechanical and Electronics Design Aspects,” in Oceans 99 MTS/IEEE Conference Proceedings, Seattle, vol. 1, September 1999. [ .pdf ]
[19]	L. Hong, T. B. Koay, J. R. Potter, and S. H. Ong, “Estimating snapping shrimp noise in warm shallow water,” in Oceanology International '99, Singapore, 1999. [ .pdf ]
[20]	J. R. Potter, “Challenges of seeing underwater -a vision for tomorrow,” in Naval Platform Technologies Seminar, Singapore, 1999. [ .pdf ]
[21]	J. R. Potter and M. A. Chitre, “Optimisation and beamforming of a two-dimensional sparse array,” in High Performance Computing 1998, vol. 1, pp. 452 - 459, November 1998. [ .pdf ]
[22]	“Cacophony of the deep (short article in Discover magazine),” Discover Magazine, vol. 19, May 1998.
[23]	J. R. Potter, “Ambient noise imaging potential for intelligent terrestrial animals,” in Singapore Acoustical Society Annual Conference, Singapore, 1998.
[24]	J. R. Potter, F. N. Wu, and L. Hong, “A planned tomographic inversion experiment for snapping shrimp; temporal and spatial statistics of these primary noise producers,” in Shallow Water Acoustics Conference, Beijing, PRC, 1997.
[25]	J. R. Potter, L. T. Wei, and M. A. Chitre, “High-frequency ambient noise in warm shallow waters,” in Sea Surface Sound, UK, 1997.
[26]	J. R. Potter, T. W. Lim, and M. A. Chitre, “Ambient noise environments in shallow tropical seas and the implications for acoustic sensing,” in Oceanology International '97, Singapore, 1997.
[27]	J. R. Potter, “A new Ambient Noise Imaging system for ANI, passive and bistatic active acoustic imaging in shallow water,” in High Frequency Acoustics in Shallow Water, Italy, 1997.
[28]	J. R. Potter, T. W. Lim, and M. A. Chitre, “Acoustic Imaging & the Natural Soundscape in Singapore Waters,” in DSO-NUS Joint R&D Seminar, Singapore, 1997.
[29]	J. R. Potter, M. A. Chitre, and E. Delory, “Whales, Dolphins & shrimp: some interests of the Acoustic Research Laboratory (ARL), National University of Singapore (NUS),” in MBARI, USA, 1997.
[30]	E. Taylor, J. R. Potter, and M. A. Chitre, “Ambient noise imaging potential of marine mammals,” in Bioacoustics Conference, Loughborough (UK), 1997.
[31]	J. R. Potter, E. Taylor, and M. A. Chitre, “Could Marine Mammals use Ambient Noise Imaging techniques ?,” in 134th Acoustical Society of America Meeting, San Diego, 1997.
[32]	M. A. Chitre and J. R. Potter, “Ambient Noise Imaging Simulation using Gaussian Beams,” in 134th Acoustical Society of America Meeting, San Diego, 1997.
[33]	M. J. Buckingham, J. R. Potter, and C. L. Epifanio, “Seeing underwater with background noise,” Scientific American, vol. 274, pp. 86-90, February 1996.
[34]	J. R. Potter and M. A. Chitre, “Statistical models for ambient noise imaging in temperate and tropical waters,” in 132nd Acoustical Society of America Meeting, Honolulu, 1996.
[35]	J. R. Potter and M. A. Chitre, “ADONIS imaging with a Kalman filter & higher-order statistics,” in 3rd European Conference on Underwater Acoustics, vol 1, p349-354, Heraklion, Greece, 1996.
[36]	J. R. Potter, S. H. Ong, Q. Ye, and F. N. Wu, “High Resolution Maximum Likelihood Estimator for Ambient Noise Imaging,” in 132nd Acoustical Society of America Meeting, Honolulu, 1996.
[37]	M. J. Buckingham and J. R. Potter, “Acoustic Daylight Imaging: Vision in the Ocean,” GSA Today, April 1994. [ .pdf ]
[38]	J. R. Potter, “Acoustic imaging using ambient noise - Some theory and simulation results,” Journal Of The Acoustical Society Of America, vol. 95, pp. 21-33, January 1994.
[39]	M. J. Buckingham and J. R. Potter, “Observation, theory and simulation of anisotropy in oceanic ambient noise fields and its relevance to Acoustic Daylight imaging,” in Sea Surface Sound 1994, California, USA, 1994.