Document qdR8EOwvGK6YExN7Mw6Ry1vKE

686 JEROME B. COX, JB. feed and discharge of the planer. These openings were made just large enoug for the wood to move in and out of the planer. A short ductlike arrangement w( attached at these openings to minimize the transmission of sound through th The top and sides of the duct were covered with a layer of glass wool. A liar glass window was installed in the wall just above the feed opening so that stih operators could see the wood as it entered the feed rolls. Doors for maintenan' work were carefully hung and gasketed to prevent sound leakage. Air ap NOISE AND THE CONSERVATION OF HEARING 687 IV ililfrjfiing system and the engine in a reasonable amount of time. ,In addition, ^`'^fllpifoise is radiated by the air intake and the cylinder casting. There- ffijpiiiayof the saw-iB the most practical- solution. tfer Ife -*>. r j tv:*, r i IUESWWS m Si? - Figure 30. An enclosure around a large planer. This view shows opening at discharge of machine. Note doors for access to interior of enclosure and moving belt that conveyS'ji through output duct. (Courtesy Kroehler Manufacturing Co.) ventilation and for the removal of wood chips passes into the enclosure th a labyrinth lined with glass wool to insure that little noise escapes through, path. This air is exhausted through a heavy duct to the roof. The noise reducjjjn obtained with an enclosure such as this depends upon the quality of workmanslfjt but should be at least 15 or 20 db in the mid-frequency range. ...... 6. jpr'the Tettxng ,pj outboard, motprs, chain saws, and other portable applications are. ustx|H|| noisy. Effective quieting is not readily achieved because these engines ,mf compact and light in weight. Therefore, the testing of these engines. .U -manufacturer-isdikely-to-ha. a severemoise .exposure for the testing ore' In one instance, chain-saw testing, small individual test cells simple solution (Figure 31). The exhaust of the engine is passed thro.ughj^ that leads to a large stationary silencer. Usually, because of the exhaust stack on the engine, it is not possible to make a tight connection be PA :t&| SJ jjfe-^.^l0!rbfViOW8 ofanfenclosurelor a chain-saw.-The duct in the top picture reduces ? otherwise travel along the path, taken by the cooling air as it leaves the ^A^fih^^t^M.Jpicture sHoW tke d.oor'at the front of the enclosure. Note the window Xwh'giiiuHliiheJshort duct for adjustment on the engine. sysX'.'i. $> K;" ` . wmm. if-,cJ1 J t{ fv-a