and third-octave positions for center band frequencies of 

 100, 200, 400, 800, and 1600 c/s. 



TABLE 1. NOISE SAMPLES SELECTED FOR ANALYSES, BY LOCATION. 

 (FOR THE BANDWIDTHS USED, SEE ABOVE) 



LOCATION 



NUMBER OF 

 NOISE SAMPLES 



NUMBER OF P D 

 CURVES OBTAINED 



FILTER USED FOR ANALYSIS OF DATA 



SOUTHERN 

 CALIFORNIA 



9 



29 



8 SAMPLES WITH ALLISON LABS FILTER; 

 1 SAMPLE WITH ALLI SON LABS AND B & K 



BERING STRAITS 



9 



24 



ALLISON LABS 



NORTH PACIFIC 



8 



65 



B&K 



SAN DIEGO 

 (SHIP NOISE 

 IN HARBOR) 



9 



36 



ALLISON LABS 



Actual probability density curves of ambient noise 

 are shown in figures 3 and 4. The large fluctuations in 

 some of the traces are caused by substantial variations in 

 the level of the noise sample. Since some of the curves 

 appeared to be closely gaussian, the methods used to 

 measure the parameters of the distribution included over- 

 lays, calculated moments, and cumulative probability 

 graphs. Tests of significance and the chi-square "good- 

 ness of fit" tests were used to determine what values of 

 skewness and kurtosis were improbable at a 5 or 1 per cent 

 probability level. 



11 



