Figure 3.--Pond half filled. 



^.A»**'f 



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Figure 4, --Gates being held up as during a sound or a control run. 



its position adjacent to section No. 1, pre- 

 dominantly because of the enveloping, non- 

 directional nature of its sound pattern. The 

 unit, designed as a sonic mine sweep, had a 

 frequency range of 67 to 3,500 c.p.s. utilizing 

 110 volts d.c. at 3 amps. In order to use the 

 full potential of the speaker, it was necessary 

 to connect two 125-watt amplifiers in tandem 

 to obtain a 200-watt power. A signal generator 

 or oscillator con^pleted the low frequency 

 equipment (fig. 7). It might be noted that 67 

 to 3,500 c.p.s. is roughly the range of a piano. 

 At a frequency of 60 to 2,000 c.p.s. at 3,000 

 dynes/cm.'^, the intensity was 70 decibels 

 above 1 dyne/cm.-' at a distance of 3 feet, 



rising to 12,000 dynes/cm. 2, or 82 db above 

 1 dyne/cm. 2, at 2,500 to 3,500 c.p.s. 



The complex interference patterns caused 

 by reflection from the surface and bottom 

 prevented a uniform fall-off of the sound 

 along the length of the trap structure and 

 also prevented accurate measurements of 

 the sound field. 



Before starting the sonic tests, we placed 

 100 trout in each of the 10 sections of the 

 trough. Fifty trout of the same stock were 

 placed in one live car near shore and several 

 large brood rainbow up to 24 inches in length 



