It mu3t be emphasized that this report is intended to describe the 

 factors which are involved in the interaction between noise and marine 

 mammals, and to explore maximal ranges of possible influence. It is not 

 intended to estimate zones of noise influence for any specific OCS locations. 



II. SOURCE-PATH-RECEIVER MODEL 



The source-path-receiver model has proved wery useful for the estimation 

 of the range to which a sound may be detected. Its greatest use has been in 

 estimating detection of underwater sounds, and accordingly, the analytic 

 expression for calculating detection range, given the proper quantitative data 

 on source, path, and receiver, is called the sonar equation (Urick, 1975). It 

 was developed for naval applications during World War II and is expressed in 

 two forms: (a) active sonar involving detection of an echo reflected from an 

 object in the ocean, and (b) passive sonar involving detection of sound 

 emitted by a source. The passive sonar model is the one used exclusively in 

 this report. 



The elements of the source-path-receiver model as used in this report 

 may be described as follows: 



A. Source 



The sound source is OCS oil- and gas-related, such as an oil 

 drilling rig, a production platform, a supply boat, an impulse noise maker for 

 seismic exploration, etc. 



G-9 



