INTRODUCTION 



The rapid increase in offshore petroleum operations during the past 

 decade, and the more rapid increase that is anticipated for the next two 

 decades, suggests that the noise generated during these operations may pose 

 serious noise pollution problems for a variety of acoustic sensors (Underwater 

 Systems, 1973). The discovery of oil in deep water and the development of 

 mobile drilling platforms, which have the capability for drilling in water 

 depths of several thousand feet, suggests that the past trend of drilling 

 platforms in a few shallow shelf regions (e.g. Gulf of Mexico) can be 

 augmented by exploration and production wells out to water depths of several 

 thousand feet. Location of these noise sources in greater water depths will 

 thus provide better acoustic coupling to deep oceanic waters. 



The acoustic environment in the area of offshore drilling activities may 

 influence the behavior and distribution of marine mammals in outer continental 

 shelf waters. The protection of wildlife and the acoustic problems relating 

 to human noise pollution form but a fraction of the whole subject that relates 

 to human-wildlife interactions (Busnel, 1978). 



There is general agreement among biologists that the acoustical sense of 

 aquatic animals probably constitutes their most important distance receptor 

 system. Studies of the acoustic activities of marine animals suggests that an 

 animal's acoustical system can, and does, provide its owner appropriate 

 information readily and rapidly, on a variety of functions relative to food, 

 competitors, potential mates and predators (Myrberg, 1978). 



Noise measurement data from offshore drilling activities are sparse. A 

 survey of the published literature and contacts with private industry revealed 

 that much of the available information is bandwidth limited. Measurements 

 that have been made were with equipment which was either limited in its 

 high-frequency response or was "rolled off" at the lower frequency limits due 

 to high ambient noise levels. Shallow water ambient noise levels in areas of 

 offshore drilling activity are also limited. In the relatively shallow waters 

 of drilling activities, the problem of multi-paths becomes significant in 

 terms of making accurate measurements. The acoustic wave may reflect off the 



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