Passive acoustic localization with an AUV-mounted hydrophone array

• Published in: The Journal of the Acoustical Society of America 2004-05, Vol.115 (5_Supplement), p.2615-2615
• Main Authors: D’Spain, Gerald L., Terrill, Eric, Chadwell, C. David, Smith, Jerome A., Zimmerman, Richard
• Format: Article
• Language: English
• Subjects: Marine
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4784798

A mid-size Odyssey IIb autonomous underwater vehicle (AUV) was retrofitted with the advanced vectored-thrust system presently installed on AUVs manufactured by Bluefin Robotics, Inc. Subsequent modifications to this thrust system decreased the radiated acoustic and vibration noise levels recorded by an eight-element hydrophone array mounted on the AUV’s inner shroud by 20 to 50 dB across the 20 Hz to 10 kHz band. This reduction in self-noise levels to near, or at, background ocean noise levels permits the use of the vehicle-mounted hydrophone array in passive ocean acoustic studies. One example is the application of passive synthetic aperture processing techniques to provide greater spatial resolution estimates of the direction of low frequency sources. Doppler spreading caused by medium motion is a limiting factor in array gain. At mid frequencies (1–10 kHz), the complexity of the received acoustic field created by scattering off the AUV body is partly captured in the array processing by the use of replica vectors measured in a calibration tank. These empirical replica vectors decrease the azimuthally dependent degradation in beamforming performance over that of plane waves. [Work supported by ONR, Code 321(US).]