Effect of Biological Activity on Broadband Passive Fathometry

Jahangir Alam, E. H. Huntington, M. R. Frater

School of Engineering and Information Technology, University College, University of New South Wales, Canberra, Australia.

DOI: 10.4236/oja.2013.32A005                

Abstract

A passive fathometer can be formed by two vertically separated hydrophones. The depth can be estimated from the Green’s function between the hydrophones, which is calculated from the cross-correlation between ocean ambient noise fields received at those two hydrophones. The performance of the fathometer depends on the signal to noise ratio (SNR) and the resolution of the noise cross-correlation function. In a given environment, improved SNR and resolution of the cross-correlation function can be achieved through longer observations, more observation points, or increasing bandwidth. Long time averaging has been demonstrated, but requires that the channel be stationary over the averaging time. Hydrophone arrays are commonly used, but result in increased cost and complexity. Recent work shows that the SNR and resolution of the correlation function can also be improved by the use of the large bandwidth noise fields. This paper shows that the non-surface biological noise generated by marine animals, such as shrimp, is one of the major issues in the performance of such a broadband passive fathometer operating in shallow water. This noise tends to occur at higher frequencies. Frequencies at which significant non-surface biological noise is present cannot be used to improve fathometer performance. Consequently, the upper limit of frequencies that can be used in a passive fathometer is limited by the lower limit of the bandwidth occupied by the biological noise.

Keywords

Passive Fathometer; Bottom Profile; Bandwidth; Shrimp; Biological Noise

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	C. H. Harrison, “Sub-Bottom Profiling Using Ocean Ambient Noise,” Journal of the Acoustical Society of America, Vol. 115, No. 4, 2004, pp. 1505-1515. doi:10.1121/1.1645854
[2]	M. Siderius, C. H. Harrison and M.B. Porter, “A Passive Fathometer Technique for Imaging Seabed Layering Using Ambient Noise,” Journal of the Acoustical Society of America, Vol. 120, No. 3, 2006, pp. 1315-1323. doi:10.1121/1.2227371
[3]	C. H. Harrison and M. Siderius, “Bottom Profiling by Correlating Beam Steered Noise Sequences,” Journal of the Acoustical Society of America, Vol. 123, No. 3, 2008, pp. 1282-1296. doi:10.1121/1.2835416
[4]	J. Traer, P. Gerstoft and W. S. Hodgkiss, “Ocean Bottom Profiling with Ambient Noise: A Model for the Passive Fathometer,” Journal of the Acoustical Society of America, Vol. 129, No. 4, 2011, pp. 1825-1836. doi:10.1121/1.3552871
[5]	P. Gerstoft, W. S. Hodgkiss, M. Siderius, C. H. Huang, and C. F. Harrison, “Passive Fathometer Processing,” Journal of the Acoustical Society of America, Vol. 123, No. 3, 2008, pp. 1297-1305. doi:10.1121/1.2831930
[6]	S. A. Albahrani, M. R. Frater and E. H. Huntington, “Linearly Filtered Estimation of the Time-Domain Greens Function from Measurements of Ambient Noise,” Journal of the Acoustical Society of America, Vol. 124, No. 5, 2008, pp. 2699-2701. doi:10.1121/1.2981049
[7]	K. G. Sabra, P. Roux and W. A. Kuperman, “Emergence Rate of the Time-Domain Greens Function from the Ambient Noise Cross-Correlation Function,” Journal of the Acoustical Society of America, Vol. 118, No. 6, 2005, pp. 3524-3531. doi:10.1121/1.2109059
[8]	S. E. Fried, W. A. Kuperman, K. G. Sabra and P. Roux, “Extracting the Local Greens Function on a Horizontal Array from Ambient Ocean Noise,” Journal of the Acoustical Society of America, Vol. 124, No. 4, 2008, pp. 183-188. doi:10.1121/1.2960937
[9]	K. G. Sabra, P. Roux, A. M. Thode, G. L. DSpain, W. S. Hodgkiss and W. A. Kuperman, “Using Ocean Ambient Noise for Array Self Localization and Self-Synchronization,” IEEE Journal of Oceanic Engineering, Vol. 30, No. 2, 2005, pp. 338-347. doi:10.1109/JOE.2005.850908
[10]	P. Roux, W. A. Kuperman and the NPAL Group, “Extracting Coherent Wave Fronts from Acoustic Ambient Noise in the Ocean,” Journal of the Acoustical Society of America, Vol. 116, No. 4, 2004, pp. 1995-2003. doi:10.1121/1.1797754
[11]	R. Snieder, “Extracting the Greens Function from the Correlation of Coda Waves: A Derivation Based on Stationary Phase,” Physical Review, Vol. 69, No. 4, 2004, 8 Pages.
[12]	R. L. Weaver and O. I. Lobkis, “Fluctuations in Diffuse Field Correlations and the Emergence of the Greens Function in Open Systems,” Journal of the Acoustical Society of America, Vol. 117, No. 6, 2005, pp. 3432-3439. doi:10.1121/1.1898683
[13]	O. I. Lobkis and R. L. Weaver, “On the Emergence of the Greens Function in the Correlations of a Diffuse Field,” Journal of the Acoustical Society of America, Vol. 110, No. 6, 2001, pp. 3011-3017. doi:10.1121/1.1417528
[14]	R. L. Weaver and O. I. Lobkis, “Elastic Wave Thermal Fluctuations, Ultrasonic Waveforms by Correlation of Thermal Phonons,” Journal of the Acoustical Society of America, Vol. 113, No. 5, 2003, pp. 2611-2621. doi:10.1121/1.1564017
[15]	J. Ricket and J. Claerbout, “Acoustic Daylight Imaging via Spectral Factorization: Helioseismology and Reservoir Monitoring,” The leading Edge, Vol. 18, No. 8, 1999, pp. 957-960. doi:10.1190/1.1438420
[16]	N. M. Shapiro and M. Campillo, “Emergence of Broadband Rayleigh Waves from Correlations of Ambient Seismic Noise,” Geophysical Research Letters, Vol. 31, 2004, Article ID: L07614.
[17]	J. Alam, M. R. Frater and E. H. Huntington, “Improving Resolution and Snr of Correlation Function with the Increase in Bandwidth of Recorded Noise Fields during Estimation of Bottom Profile of Ocean,” Sydney, 2010.
[18]	D. H. Cato and M. J. Bell, “Ultrasonic Ambient Noise in Australian Shallow Water at Frequencies up to 200 khz,” Technical Report, DSTO Materials Research Laboratory, Urbana, 1992.
[19]	K. Wapenaar, J. Thorbecke and D. Draganov, “Relations between Reflection and Transmission Responses of Three-Dimensional Inhomogeneous Media,” Geophysical Journal International, Vol. 156, No. 2, 2004, pp. 179-194. doi:10.1111/j.1365-246X.2003.02152.x
[20]	M. R. Liewen and W. K. Melvile, “A Model of the Sound Generated by Breaking Waves,” Journal of the Acoustical Society of America, Vol. 90, No. 4, 1991, pp. 2075-2080. doi:10.1121/1.401634
[21]	G. B. Deane, “Sound Generation and Air Entrainment by Breaking Waves in the Surf Zone,” Journal of the Acoustical Society of America, Vol. 102, No. 5, 1997, pp. 2671-2689. doi:10.1121/1.420321
[22]	G. M. Wenz, “Acoustic Ambient Noise in the Ocean: Spectra and Sources,” Journal of the Acoustical Society of America, Vol. 34, No. 12, 1962, pp. 1936-1956. doi:10.1121/1.1909155
[23]	D. H. Cato and R. D. McCauley, “Australian Research in Ambient Sea Noise,” Acoustics Australia, Vol. 30, No. 1, 2002, pp. 13-20.
[24]	M. J. Hinich, “Processing Spatially Aliased Arrays,” Journal of the Acoustical Society of America, Vol. 64, No. 3, 1978, pp. 792-794. doi:10.1121/1.382044
[25]	V. O. Knudsen, R. S. Alford and J. W. Emling, “Underwater Ambient Noise,” Journal of Marine Research, Vol. 7, 1948, pp. 410-429.
[26]	V. O. Knudsen, R. S. Alford and J. W. Emling, “Survey of Underwater Sound, Report No. 3, Ambient Noise,” Office of Scientific Research and Development, National Defence Research Committee, Washington DC, 1944.
[27]	F. B. Jensen, W. A. Kuperman, M. B. Porter and H. Schmidt, “Computational Ocean Acoustics,” American Institute of Physics, New Work, 1994.