Improved time-delay estimates of underwater acoustic signals using beamforming and prefiltering techniques

• Published in: IEEE journal of oceanic engineering 1989-07, Vol.14 (3), p.238-244
• Main Author: Ferguson, B.G.
• Format: Article
• Language: English
• Subjects: acoustic arrays; Acoustic noise; Acoustic waves; Acoustics; Amplitude estimation; Array signal processing; delay; Delay effects; Delay estimation; Exact sciences and technology; filtering; filters; Frequency domain analysis; Fundamental areas of phenomenology (including applications); hydrophones; Marine; noise; Noise reduction; Physics; signal processing; signal transmission; Sonar equipment; spectral analysis; Underwater acoustics; Underwater sound
• ISSN: 0364-9059; 1558-1691
• DOI: 10.1109/48.29601

Passive sonar systems that localize broadband sources of acoustic energy estimate the difference in arrival times (or time delays) of an acoustic wavefront at spatially separated hydrophones, The output amplitudes from a given pair of hydrophones are cross-correlated, and an estimate of the time delay is given by the time lag that maximizes the cross correlation function. Often the time-delay estimates are corrupted by the presence of noise. By replacing each of the omnidirectional hydrophones with an array of hydrophones, and then cross-correlating the beamformed outputs of the arrays, the author shows that the effect of noise on the time-delay estimation process is reduced greatly. Both conventional and adaptive beamforming methods are implemented in the frequency domain and the advantages of array beamforming (prior to cross-correlation) are highlighted using both simulated and real noise-field data. Further improvement in the performance of the broadband cross-correlation processor occurs when various prefiltering algorithms are invoked.< >