For all other trials the wampus was placed 

 where the visual and mechanical stimuli were 

 minimized or absent. The powerful jets from 

 the turbine were directed so that they did not 

 impinge upon the structure or the fish. Upon 

 one occasion, the transducer was inadvertently- 

 shifted so that a stream of turbulent water was 

 directed into section No. 1. The trout imme- 

 diately oriented themselves in an upstream 

 fashion. At least one fish dashed into the jet 

 and flipped at the surface as though feeding 

 upon particles carried by the current. The 

 majority remained at a distance of approxi- 

 mately 12 feet in a normal schooling pat- 

 tern. 



Small turtles, frogs, toads, snails, and 

 assorted aquatic insects were kept in live 

 boxes during the trials. The pond was heavily 

 populated with frogs and snails at all times. 

 None of the organisnns appeared to notice the 

 sound. Even when the live box containing them 

 was placed within 8 inches of the wampus 

 (above the jets) they made no struggle or 

 attempt to avoid the sound. Some of the small 

 brown trout became quiescent when their cage 

 was placed in close proximity to the noise, 

 and remained on the bottom resting partially 

 on their sides or on their fins as though 

 exhausted. When they were removed, they 



resumed their norn^al swimming movements 

 and appeared unaffected. All test aninnals, 

 especially the fish, were carefully watched 

 for injuries and abnornaalities, but none ap- 

 peared. 



Calibrations, or measurements of the sound 

 field intensity were nnade using standard 

 hydrophones (Barcroft, Q-4, No. 29). The 

 receiver was suspended near the midpoint 

 of each section or compartment to give the 

 readings shown in tables 1-3. 



Without air, the wampus seemed to produce 

 a noise of greater intensity as judged fronn 

 the hydrophone readings. When the air to the 

 sound head was cut off, the sound escaping 

 fronn the water changed from a throaty roar 

 to a metallic hammering. This difference, 

 and the measurement of it, is the result of a 

 change from a loudness level to an intensity 

 level- -the difference between the boom of a 

 cannon and the crack of a rifle. The wampus 

 trials were then discontinued. 



Again, contingency tests between sound trials 

 and controls showed highly significant dif- 

 ferences of distributions of fishes within the 

 trough. No indication, however, that sound 

 caused the differences was evident. 



TABLE 1. — Sound field Intensity produced by "wampus" at 100 pounds air pressure 



and 60 poxmds of water pressure. 



A convenient way to express the output of a hydrophone in terms of the acoustic input 

 is by stating the number of microvolts response per dyne per square centimeter. Hydro- 

 phones are constructed so that the sensitivity thus expressed is independent of the power 

 input and the frequency of the sound. 



27 



