Vibration induced in towed linear underwater array cables

Towed linear arrays of hydrophones are used in various applications, for example, seismic prospecting. Tow cable vibration is capable of causing output in the towed array system. Since one of the factors limiting acoustic sensitivity is self-noise, the general objective of this analysis is to investigate the nature of longitudinal and transverse cable vibrations, with the aim of minimizing vibration transmitted to the array. The equations of transverse cable motion are derived and solved for a single-póint excitation and for distributed-vortex excitation. The response to vortex-shedding excitation along the first 150 ft of array-end cable is quantitatively evaluated and compared with actual tow-trial measurements. Two types of longitudinal vibration are analyzed, one caused by direct excitation along the cable axis, and one caused indirectly by transverse cable vibration. Fluid drag and hysteretic damping are included in the analysis.