BS EN ISO 5136:2009

1   Scope

   1.1   General 
   This International Standard specifies a method for testing ducted fans and other air-moving
     devices to determine the sound power radiated into an anechoically terminated duct
     on the inlet and/or outlet side of the equipment. 
   
       NOTE 1  For the sake of brevity, wherever the term “fan” occurs in the text, it means “fan
        or other air-moving device”. 
   
   The method is applicable to fans which emit steady, broad-band, narrow-band and discrete-frequency
     sound and to air temperatures between – 50 °C and + 70 °C. The  test duct  diameter range is from 0,15 m to 2 m. Test methods for small ( d  < 0,15 m) and large ( d  > 2 m)  test ducts  are described in the informative Annexes H and I, respectively. 
   The maximum mean flow velocity at the microphone head for which the method is suitable
     depends on the type of  microphone shield  used, and is as follows: 
   

         
            
            
            
         
         
            
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