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measuring the sound of several boats. They found that the river was an 

 inherently noisy environment— moving water, rapids and wind. The noise from 

 passing power boats was comparable to the level produced by other recreation 

 vehicles on the noisy end of the scale, such as motorcycles and jeeps. 

 Manufacturers they talked to were highly skilled and motivated, but little 

 acoustic engineering had been applied to their boats. The builders, however, 

 were very interested in learning about the acoustic technology that could make 

 their boats less impactive and more competitive in the recreation boat market. 

 Among Harrison's recommendations was the conduct of a seminar on the basics 

 of noise control. 



The Northwest Power Boat Association and Forest Service sponsored a 

 sound seminar for boat builders in November of 1991, assisted by acoustical 

 specialists from the Technology and Development Center and a private acoustic 

 testing firm. As a direct result of this session, the Welded Aluminum Boat 

 Manufacturers Association (WABMA) was formed to facilitate the 

 commimication of technology and to conduct comprehensive acoustical tests of 

 jet boats of various sizes and design. Tests would be designed to provide 

 information that could be used by manufacturers to cut noise levels of their 

 craft, reducing the impact of noise on the boat's occupants and other river users. 



The studies were conducted as a cooperative project in 1993, with the 

 WABMA, Forest Service, State of Idaho, State of Oregon and Nez Perce 

 County participating. The data was used by manufacturers to make their craft 

 quieter; progress in acoustical tuning of jet boats continues today. A November 

 14, 1993 Lewiston Morning Tribune article quoted acoustic expert Harrison as 

 saying that testing showed a drop of 6 decibels in just the last year. "The boats 

 are phenomenally quieter than just over a year ago. That's like having a quarter 

 as many boats on the river ." (emphasis added) 



A Forest Service manager on the Salmon River mentioned that he talked 

 with floaters during the 1995 season who were amazed at how quiet many of 

 the jet boats had become. They couldn't hear the boats any more before they 

 appeared. Boaters on the Snake had that same experience, with newer craft 

 difficult to hear over the river's natural sounds. The loudest noise from some 

 craft is made by the water sliding across or slapping the hull. This is due to 

 better mufflers, acoustical insulation in engine compartments, isolation of 

 engines and pumps from the hull and other measures identified by the tests. 



WABMA's members haven't slowed down. Another seminar was held after 

 the testing. Now they are establishing industry guidelines, and a certification 

 program for new boats, that will exceed the standards of ^very state in our 

 Nation. Some older boats on the river are still relatively noisy. However, as 

 they replace mufflers to comply with Forest Service requirements they will 



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