interest and to observe cyclical trends. Based on the information 

 obtained, specialized programs with specialized equipment may be under- 

 taken on subject matters of interest. 



The work on marine animal sounds is supported in part by the 

 Biology Branch of the Office of Naval Research and in part by Bell 

 Telephone Laboratories under a contract with the Sonar Branch of the 

 Bureau of Ships. Work on sound propagation and ambient noise is sup- 

 ported in part by the Acoustics Branch of the Office of Naval Research 

 and in part by the Applied Sciences Branch of the Bureau of Ships . 

 Laboratory space and facilities are provided by the Lerner Marine 

 Laboratory, a Field Station in Biology of the American Museum of Natural 

 History. The following factors entered into the selection of Bimini for 

 the installation: the relatively short cable length required to reach 

 the waters of the Gulf Stream; the clarity of the water; the availability 

 of the Lerner Laboratory; the island's easy accessibility from Miami. 



This report is intended to describe the characteristics of 

 the system and the installation procedure, which involved some special 

 techniques. The aim is to include enough detail to provide information 

 for individuals concerned with the system or the results obtained. A 

 summary of the preliminary observations is also given. 



3. Overall System. 



A chart of the area between Miami and Bimini is shown in 

 Figure 1. Depth readings are in fathoms. The west coast of Bimini may 

 be seen in more detail in Figure 14, along with the hydrophone locations, 



A schematic outline of only the major functional capabilities 

 of the fixed system installation at Bimini is contained in Figure 2. 

 More detailed information appears later in the report under sections 4, 

 5 , and 6 . 



4. Hydrophones and Preamplifiers. 



(a) Hydrophones 



Two PZT (lead zirconate) hydrophones, type 2Z-110, serial 

 numbers 2Z-113 and 2Z=116, and associated preamplif ers , were supplied 

 by the Bell Telephone Laboratories, Whippany, New Jersey. They are 

 encased in stainless-steel protective cages which also contain the 

 transistorized preamplifiers. Fiberglass screening was wrapped around 

 the cage to reduce the flow of water over the hydrophone and the result- 

 ing flow noise. 



The active element of the hydrophone consists of two series 

 connected lead zirconate crystal rings. The rings are cemented to 

 metal end pieces with epoxy resin. The end piece which serves as a 



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