ABSTRACT 



An experimental investigation was conducted to determine the sources 

 and methods of reducing cable vibrations in acoustic measuring systems, to 

 provide information concerning full-scale towing behavior, and to accurately 

 define the towing configuration of such systems. The results of this investi- 

 gation including comparisons with theory and recommendations for improving 

 towed acoustic systems are given in this report. 



INTRODUCTION 



The use of towed hydrophone systems to measure radiated noise from 

 submarines has led to many problems which must be alleviated if such 

 systems are to fully serve their purpose. Specifically, the vibration of the 

 cables is believed to be one of the major sources of the high level of back- 

 ground noise in the low frequency bands which has been associated with such 

 measurements. Furthermore, insufficient data concerning the resistance of 

 these kinds of arrays have made it difficult to determine the configuration of 

 the array and, consequently, the orientation of the hydrophones. 



Accordingly, an experimental program was established under the Funda- 

 mental Hydromechanics Program at the David Taylor Model Basin to study 

 the cause and effects of these flow-created problems as they pertain to typical 

 surface-suspended hydrophone systems. The specific objectives of the pro- 

 gram were: to investigate the capabilities of such systems with regard to 

 speed, depth, and steadiness of tow; to determine how well the behavior of 

 full-scale systems can be predicted for a range of operable conditions; and 

 to provide information which is required to accurately define the configuration 

 of a given system . 



The facilities which are necessary to carry out tests of a complete system 

 under highly controlled conditions and at a large enough scale required for 

 accurate representation are not available. Consequently, the approach used 

 was to carry out the program in the following three phases: shallow-water 

 towing tests in the towing basins at the Taylor Model Basin to determine sources 

 and magnitudes of low-frequency noise components in the acoustic system, open- 

 water tests in the Chesapeake Bay to provide data on the effects of cable scope 

 and fairing on vibrations and towing attitude of the system, and tests at sea to 

 evaluate the characteristics of a full-scale system proposed for submarine 

 radiated-noise measurements . 



This report describes the various experimental investigations, presents 

 the results of measurements to determine vibration characteristics, and in- 

 cludes pertinent observational data. The towing configuration of a proposed 

 system is briefly described, and curves and sketches are provided to define its 

 towing configuration. Recommendations are made on how to improve such 

 systems as well as for future studies which are necessary for further devel- 

 opment . 



