Experimental study on horizontal large-spacing coherence of a single mode in shallow water

• Published in: Applied acoustics 2024-05, Vol.221, p.110020, Article 110020
• Main Authors: Zhai, Duo, Zhang, Bo, Li, Fenghua, Yu, Xiaotao, Zhang, Qingqing
• Format: Article
• Language: English
• Subjects: Shallow water; Single-mode; Spatial coherence; Spatial correlation coefficient; Warping transformation
• ISSN: 0003-682X; 1872-910X
• DOI: 10.1016/j.apacoust.2024.110020

The spatial coherence of acoustic pressure fields would affect the design of large-aperture sonar systems. The experimental data at low frequencies propagating in approximately 100 m depth water from explosive sources to a bottom-resting hydrophone is analyzed to study the horizontal spatial coherence. Sound paths are about 80 km both in the along-shore direction and in the cross-shore direction. The theoretical analysis interprets that the signals of a single mode after compensating the modal phase would have higher correlation coefficients than the signals including all modes. The warping transformation is used to filter the modes. The experimental results show that the coherence length of a single mode can reach more than 100 km, which corresponds to about 2700–16000λ due to the frequency. The high correlation of a single mode indicates that it is possible to perform coherent processing on large-aperture arrays or distributed arrays with a maximum horizontal size much larger than the existing array apertures in shallow water. •The theoretical analysis interprets that the signals of a single mode would have higher correlation coefficients.•The experimental results show that the coherence length of a single mode can be about 2700-16000λ.•The high correlation of a single mode indicates that it is possible to perform coherent processing on large-aperture arrays.