Deep- Water Tests at Lake Pend Oreille, Idaho 



As the limitations of the small tank precluded meaningful 

 measurements in the low-frequency region, arrangements 

 were made for calibration measurements at the NEL Pend 

 Oreille Calibration Station in Idaho (fig. 9). Months of 

 preparation were necessary to obtain high-speed underwater 

 photographs of the bubble development down to a depth of 

 300 feet below the surface, simultaneously with sound- 

 pressure and frequency measurements. The problems of 

 adequate lighting and synchronizing were sizable. 



» J. 



Figure 9. Installation at Lake Pend Oreille for deep-water 

 tests, showing extension dock used to lower power and control 

 cables into water. Small float in foreground holds trans- 

 formers for boosting shore power to barge. 



25 



