Electrical and Computer Engineering

Electrical and Computer Engineering

History

Research into acoustics at the University of Canterbury started with the arrival of Professor Leslie Kay in the mid 1960s. His work then encompassed both ultra-sonic air acoustics and underwater acoustics. He is most well-known for his work in medical acoustics including aural aids for the blind [1,2,3,4,5,6,7,8] culminating in his being awarded the Saatchi and Saatchi Prize for Innovation in 1999 for his lifetime contribution to the field. His underwater work included some early attempts at diver's aids using lightweight portable sonar [9,10]. In 1980 Dr Peter Gough returned to New Zealand from the US [11] and began collaborating with Professor Kay on a wide-bandwidth, continuous-time, frequency modulated (CTFM) sonar build with a grant from Edo Western Corp., USA. This CTFM side scan sonar had a number of unique features including constant beamwidth over a 50kHz band. The project made some progress with classifying seafloor objects from their frequency signatures [12,13,14].

In the mid-1980s, Gough started experimenting with synthetic aperture sonar (SAS) [15]. Folk-law at the time claimed that the underwater medium would be too unstable for the required processing. One early SAS prototype built using CTFM techniques was taken to Scotland and showed that the acoustic environment was far more stable than folk-law had intimated [16,17,18]. At this time Mike Hayes was a graduate student in the department and published the first PhD thesis from Canterbury on SAS. In a particularly exciting sea trial, Gough and Hayes lost the sonar on some underwater obstructions and, after collecting the insurance money, started designing and building the second prototype. In 1994 with graduate student Ken Johnston, Gough and Hayes started looking at autofocussing techniques using nothing but the detected echoes as input [19]. This work continues to this day.

Since low(ish) frequencies and high relative bandwidths were then seen to be important for SAS to work under realistic towing conditions, several papers and thesis were published on broad-band projector design [14]. In 1996 graduate student David Hawkins produced a finite-element analysis that showed that the square head transducer element was the key to the performance and efficiency of the Tonpiltz transducer over a broad band at a centre frequency 30kHz. They named the upperband resonance of the element, the "flapping head mode" and this term has come into wide spread use for this type of element [20]. Hawkins continued to work with the completed second prototype and modified a whole suite of modern efficient SAR algorithms to work with SAS data [21,22]. This work was all published as part of his PhD thesis [21].

In 1998, Dr Michael Hayes rejoined the group after several years in industry and immediately redesigned the data recording system of the second SAS to a fully digital system. This is the SAS still in use today although plans are well in hand for the third prototype with multiple hydrophones due to be finished by the end of 2001.

Over the years grants and contracts have been received from the New Zealand Defence Science Establishment, Marconi Underwater Systems Laboratory (UK), the Maritime Division of Hughes Aircraft Corporation (now owned by Raytheon Electronic Systems), the Defence Science and Technology Organisation (Australia), and the Office of Naval Research (USA), as well as significant support from the Department of Electrical and Computer Engineering, and the University of Canterbury.

Bibliography
  1. L. Kay and M. A. Do, "An artificially generated multiple object auditory space for use where vision is impaired," Acustica, vol. 36, pp. 1-8, December-January 1976/7.
  2. L. Kay, J. T. Boys, G. R. S. Clark, and J. L. Mason, "The echocardiophone: a new means of observing spatial movement of the heart," Ultrasonics, vol. 15, pp. 136-41, May 1977.
  3. L. Kay, S. T. Bui, J. A. Brabyn, and E. R. Strelow, "Single object sensor: a simplified binaural mobility aid," Visual Impairment and Blindness, vol. 71, pp. 210-3, May 1977.
  4. L. Kay, E. R. Strelow, and N. Kay, "The use of electronic spatial sensors in the training of blind children," Visual Impairment and Blindness, vol. 71, pp. 174-5, April 1977.
  5. R. M. Hodgson and J. T. Boys, "A novel prosthetic sonar," Ultrasonics, vol. 15, pp. 99-100, May 1977.
  6. J. T. Boys, J. L. Mason, and R. M. Hodgson, "Improved c.w.f.m. sonars with aural displays," Ultrasonics, vol. 16, pp. 123-6, May 1978.
  7. L. Kay, N. Kay, J. Sinton, and A. de Roos, "Characterization of surface and volume structure using an air sonar with auditory display for the blind," in Ultrasonics Intnl. 81 Conf., (Guildford), pp. 38-41, 1981.
  8. L. Kay, "Electronic aids for blind persons: an interdisciplinary subject.," IEE Review Part A, vol. 131A, pp. 559-76, September 1984.
  9. A. de Roos, L. Kay, M. J. Cusdin, and A. N. Vernon, "A sonar aid for divers using binural displays," in Ultrasonics Intnl. 81, (Guildford), pp. 171-5, IPC Science and Technology Press, 1981.
  10. A. de Roos, M. J. Cusdin, and L. Kay, "A diver's sonar with auditory display," in IPENZ, vol. 10, pp. 55-8, July 1983.
  11. P. T. Gough, "Side-looking sonar or radar using phase difference monopulse techniques: coherent and non-coherent applications," Proceedings of the IEE, vol. F-130, pp. 392-98, August 1983.
  12. A. d. R. P. T. Gough and M. J. Cusdin, "Continuous transmission fm sonar with one octave bandwidth and no blind time," Proceedings of the IEE, vol. F-131, pp. 270-74, June 1984.
  13. A. de Roos, J. J. Sinton, P. T. Gough, W. K. Kennedy, and M. J. Cusdin, "The detection and classification of objects lying on the seafloor," Journal of the Acoustics Society of America, vol. 84, pp. 1456-77, October 1988.
  14. P. T. Gough and J. S. Knight, "Wide bandwidth, constant beamwidth acoustic projectors: a simplified design procedure," Ultrasonics, vol. 27, pp. 234-38, July 1989.
  15. P. T. Gough, "A synthetic aperture sonar capable of operating at high speed and in turbulent media," IEEE Journal of Oceanic Engineering, vol. OE-11, pp. 333-39, April 1986.
  16. P. T. Gough and M. P. Hayes, "Measurements of acoustic phase stability in Loch Linnhe, Scotland," Journal of the Acoustics Society of America, vol. 86, pp. 837-839, August 1989.
  17. P. T. Gough and M. P. Hayes, "Test results using a prototype synthetic aperture sonar," Journal of the Acoustics Society of America, vol. 86, pp. 2328-2333, December 1989.
  18. M. P. Hayes and P. T. Gough, "Broadband synthetic aperture sonar," IEEE Journal of Oceanic Engineering, vol. 17, pp. 80-94, January 1992.
    Invited paper.
  19. K. A. Johnson, M. P. Hayes, and P. T. Gough, "A method for estimating the sub-wavelength sway of a sonar towfish," IEEE Journal of Oceanic Engineering, vol. 20, pp. 1-9, October 1995.
  20. D. W. Hawkins and P. T. Gough, "Multi-resonance design of a tonpilz transducer using the finite element method," IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 43, pp. 782--790, September 1996.
  21. D. W. Hawkins, Synthetic Aperture Imaging Algorithms: with application to wide bandwidth sonar.
    PhD thesis, Department of Electrical and Electronic Engineering, University of Canterbury, October 1996.
  22. P. T. Gough and D. W. Hawkins, "Imaging algorithms for a strip-map synthetic aperture sonar: Minimizing the effects of aperture errors and aperture undersampling," IEEE Journal of Oceanic Engineering, vol. 22, pp. 27-39, January 1997.