DC FAN

   The Measurements of noise levels are made in accordance with CNS 8T 53 ( which is very close to DIN 45635 )

 in a sound proof chamber with a sound level  Lp<15dBA.

   A microphone is placed 1 meter from the center line of the fan under test which is supported on elastic mounts

 in the center of test room. The fan is then run free blowing without resistance to airflow.

   Sound Pressure Level (SPL) is environmentally dependent and Sound Power Level (PWL) are defined as

             SPL = 20 log 10 P/Pref       and        PWL= 10 log 10 W/Wref   

   P=Pressure    Pref= A reference pressure   W=Acoustic power of the source    Wref=An acoustic reference power

   Fan noise data is usually plotted as Sound Power Level against the octave frequency band