The values of the observed noise level should be reasonably constant within 

 each run and should agree reasonably with the estimated noise level. A dis- 

 crepancy of 10 dbs would indicate possible error whereas a discrepancy of 20 

 dbs would indicate probable error. The values of the estimated and observed 

 noise levels* are shown with the data points on the experimental curves . 



The following is a list of all the calibration changes and consequent adjustments 

 of data points made on Channel 1 . 



Run 1 - Adjusted data points and ONL in agreement with a 



uniform S(f) = -38/-34/-33 instead of -18/-14/-13. 



Run 2 - No change . 



Run 3 - No calibration change . Assumed incorrect attenuator 

 setting (decreased transmission loss) at ranges less 

 than 11 kiloyards . 



Run 4 - Adjusted data points and ONL in agreement with a 



uniform S(f) = -38/-34/-33 instead of -48/-44/-42. 



Run 5 - (A) 1300 cps: Used S(f) = (-44) at times before 1819 

 (Reel 18) and S(f) = (-24) thereafter. 



3000 cps: Used S(f) = (-43) through Reel 18, and 

 S(f) = (-23) for Reel 19 et seq. 



700 cps: Used S(f) = (-48) through Reel 18, and 

 S(f) = (-28) for Reel 19 et seq. 



(B) Adjusted data points and ONL in agreement with a 

 uniform S(f) = -38/-34/-33 wherever -48/-44/-43 

 had been used . 



Run 6 - No change . 



3. DATA REDUCTION 



On a 15-minute cycle, the signals occurring in a 5-minute period were measured, 

 the linear deflections (mm) averaged and this average expressed in db re 1 mm. 

 This value was used in the calculation of the transmission loss as outlined above 

 for the average range during this 5-minute interval. Range was calculated from 

 the travel time of the acoustic signal and the velocity of sound. The experimental 

 data are compared with theoretical predictions in the curves of transmission loss 

 versus range contained in the body of this report. In addition, eleven experimental 

 curves were analyzed on a ping by ping basis . These are presented along with the 

 54 curves based on averaged data . 



* Indicated by (~) . 



C-9 



Arthur ZD.IUttleJnr. 



