The representation of a broadband vector field

Abstract

Compared to a scalar pressure sensor, a vector sensor can provide a higher signal-to-noise ratio (SNR) signal and more detailed information on the sound field. Study on vector sensors and their applications have become a hot topic. Research on the representation of a vector field is highly relevant for extending the scope of vector sensor technology. This paper discusses the range-frequency distribution of the vector field due to a broadband acoustic source moving in a shallow-water waveguide as the self noise of a surface ship, and the vector extension of the waveguide impulse response measured over a limited frequency range using an active source of known waveform. From theory analysis and numerical simulation, the range-frequency representation of a vector field exhibits an interference structure qualitatively similar to that of the corresponding pressure field but, being quantitatively different, provides additional information on the waveguide, especially through the vertical component. For the range-frequency representation, physical quantities that can better exhibit the interference characteristics of the waveguide are the products of pressure and particle velocity and of the pressure and pressure gradient. An image processing method to effectively detect and isolate the individual striations from an interference structure was reviewed briefly. The representation of the vector impulse response was discussed according to two different measurement systems, also known as particle velocity and pressure gradient. The vector impulse response representation can not only provide additional information from pressure only but even more than that of the range-frequency representation.

Keywords

acoustic waveguide / vector field; range-frequency interference structure / striation processing / impulse response / normal mode

References

[1] Brekhovskikh LM, Lysanov YP (2003). Fundamentals of Ocean Acoustics. Springer, 3rd edition.

[2] Chuprov, SD (1982). Interference structure of a sound field in a layered ocean. Acoustics of the Ocean: Current Status, 71–91. (in Russian)

[3] Cray B.A., Nuttall A.H. Directivity factors for linear arrays of velocity sensors. J. Acoust. Soc. Am., 2001, 110(1): 324-331

[4] Frangi AF, Niessen WJ, Vincken KL, Viergever MA (1998). Multiscale vessel enhancement filtering. Medical Image Computing and Computer-Assisted Interventation.

[5] Hawkes M., Nehorai A. Acoustic vector-sensor beamforming and Capon direction estimation. IEEE J. Oceanic Eng., 1998, 46(9): 2291-2304

[6] Hawkes M., Nehorai A. Effects of sensor placement on acoustic vector sensor array performance. IEEE J. Oceanic Eng., 1999, 24(1): 33-40

[7] Hawkes M., Nehorai A. Acoustic vector-sensor processing in the presence of a reflecting boundary. IEEE Transactions on Signal Processing, 2000, 48(11): 2981-2993

[8] Hawkes M., Nehorai A. Effects of sensor placement on acoustic vector sensor array performance. IEEE J. Oceanic Eng., 2001, 24(1): 33-40

[9] Hawkes M., Nehorai A. Wideband source localization using a distributed acoustic vector-sensor array. IEEE Transactions on Signal Processing, 2003, 51(6): 1479-1491

[10] Hermand JP and Le Gac JC (2008). Subseafloor geoacoustic characterization in the kilohertz regime with a broadband source and a 4-element receiver array. Proc. OCEANS’ 08, Quebec City, QC.

[11] Hermand J.P. Broad-band geoacoustic inversion in shallow water from waveguide impulse response measurements on a single hydrophone: theory and experimental results. IEEE J. Oceanic Eng., 1999, 24(1): 41-66

[12] Hui J.Y., Hui L., Yu H.B., Fan M.Y. Study on the physical basis of pressure and particle velocity combined processing. Acta Acustica, 2000, 4: 303-307

[13] Hursky P., Siderius M. Using ambient noise and vector sensor arrays to form a subbottom profiler. J. Acoust. Soc. Am., 2006, 120(1): 3027

[14] Jensen FB, Kuperman WA, Porter MB, Schmidt H (1994). Computational Ocean Acoustics (Modern Acoustics and Signal Processing), American Institute of Physics.

[15] Koch R.A. Proof of principle for inversion of vector sensor array data. J. Acoust. Soc. Am., 2010, 128(2): 590-599

[16] Leslie C.B. Hydrophone for measuring particle velocity. J. Acoust. Soc. Am., 1956, 28(4): 711-715

[17] Lindeberg Y (1996). Edge detection and ridge detection with automatic scale selection. In Conf. on Comp. Vis. and Pat. Recog.

[18] Liu W, Li Y, Piao SC (2009). Study on correlation processing for acoustic vector signals in underwater sound channel. The 10th Western Pacific Acoustics Conference, Beijing, China.

[19] Osler J.C., Chapman D.M.F., Hines P.C. Measurement and modeling of seabed particle motion using buried vector sensors. IEEE J. Oceanic Eng., 2010, 35(3): 516-537

[20] Petnikov VG, Kuz’kin K (2002). Shallow water variability and its manifestation in the interference pattern of sound fields. AIP Conference Proceedings, 207–217.

[21] Porter (1997). The KRAKEN normal mode program. http://oalib.hlsresearch.com/Modes/AcousticsToolbox/manual_html/kraken.html [available online].

[22] Ren QY, Hermand JP, and Piao SC (2011). The interference phenomena of the broad-band vector field and striation processing. 4th Underwater Acoustic measurements: Techniques and Results, Greece

[23] Santos P, Rodriguez OC, Felisberto P, Jesus SM, Faro P (2009). Geoacoustic matched-field inversion using a vertical vector sensor array. 3rd International Conference and Exhibition on Underwater Acoustic Measurements Technologies and Results., Greece.

[24] Santos P., Felisberto P., Jesus S.M. Vector sensor arrays in underwater acoustic applications. Emerging Trends in Technological Innovation: First IFIP WG 5.5/SOCOLNET Doctoral Conference on Computing, Electrical and Industrial Systems, 2010, Costa de Caparica, Portugal: DoCEIS 2010

[25] Shchurov V.A. Vector acoustics of the ocean, 2006, Vladivostk: Dalhauka

[26] Stojanovic M., Catipovic J.A., Proakis J.G. Reduced-complexity spatial and temporal processing of underwater acoustic communication signals. J. Acoust. Soc. Am., 1995, 98: 961-972

[27] Wong K.T., Zoltowski M.D. Extended-aperture underwater acoustic multisource azimuth/elevation direction-finding using uniformly but sparsely spaced vector hydrophones. IEEE J. Oceanic Eng., 1997, 22(4): 659-672

[28] Yang T.C. Temporal resolutions of time-reversal and passive phase conjugation for underwater acoustic communications. IEEE J. Oceanic Eng., 2003, 28: 229-245