>» 

 ■o 



Q. 

 (T 

 O 

 CO 



m 



< 



.01 - 

 .007 - 

 .005 - 



.003- 

 .002 - 



400 

 300 



200 

 150 

 100 

 75 



■ 50 

 ■■ 35 



25 

 20 



14 

 12 



10 

 4 8 



+ 5 



4 

 3.5 



• 2 



• I 



FREQUENCY 

 (kc) 



ACOUSTIC ABSORPTION COEFFICIENT NOMOGRAM 



by J. A. DORR, Underseas Division 

 Westinghouse Defense and Space Center 

 Baltimore, IVId. 



.001 



J 



This nomogram is constructed for determination of acous- 

 tic absorption coefficient values for ocean depths to 4,500 

 fathoms, from 1 to 400 kilocycles at sea water temperature 

 of 3° Celsius and 35% salinity. The nomogram was derived 

 from equation 9 (shown below) of the paper by M. Schulkin 

 and H. W. Marsh, Absorption of Sound in Sea Water, J. 

 Brit, IRE, Vol. No. 6, June 1963. In the equation below 



Ft = 21.9 X 10 



1520 



T + 273 



-■ 4500 



1 



-■ 4000 

 -■ 3500 



3000 



2500 



2000 



1500 

 1000 

 500 

 



AVERAGE 



PROPAGATION 



DEPTH 



(fms) 



a is absorption coefficient in nepers per meter; Ft is relaxa- 

 tion frequency in KG/ sec. 



T is temperature in degrees Celsius; S is salinity in parts/ 

 thousand; P is pressure in atmosphere; F is the independent 

 variable in KC/ second; 3° temperature value permits esti- 

 mating absorption coefficients for both acoustic transmis- 

 sion vertically through the water column and horizontally 

 at depths where the water temperature is less than about 

 10°. 



«=P 



.3 4 X IQ-^FtF' 



F.*-f F» 



154 



+ 



3.38 X 10 



—J X {1 - 



6.54 X lO-'P) 



