HERSEY: INTRODUCTION TO LOW-FREQUENCY PROPAGATION AND NOISE VJORKSHOP 



available to all members of the workshop well before the meeting. A 

 small editorial staff will be responsible for final editing, produc- 

 tion, and distribution of the planning guide. A record will be kept 

 of the discussions at the second plenary session, but no useful 

 decision can be made at present about its publication. 



So much for generalities. In the next 4 days we will be review- 

 ing some things old and some things new that represent our partial 

 understanding of the characteristic behavior of low-frequency sound 

 waves in and below the oceans. Low frequency here means the range 

 from 1 to 1,000 Hertz. A quite arbitrary range which, unfortunately 

 perhaps, includes at low frequencies the Airy wave of the deep ocean 

 basins and at high frequencies phenomena that are sensitive to rather 

 fine details of water structure and ocean floor topography. The past 

 emphasis in research and applications is most uneven. Major U.S. 

 emphasis has been on the spectral region from 20 to 150 Hz with some 

 far less intense emphasis on the region from 150 to 1,000 Hz. Only in 

 the past 3 or 4 years have we attempted anything significant below 20 

 Hz. Thus, we will find - if we look - that there is great unevenness 

 in our information throughout this spectrum. In some areas of interpre- 

 tation, there is great scope for speculation, because there is so 

 little hard data; whereas in others we have so much information that 

 the knowledgeable interpreter may feel tongue-tied. In the next 

 6 months — and a lot longer — we should look at the spectrum 

 encompassing both extremes in order to learn what is going on in the 

 ocean, thus solving many of the practical problems of warfare there — 

 and other marine concerns of mankind as well. 



All nations represented here use their knowledge of ocean 

 acoustics more or less intensely for some or all of the following 

 purposes : 



