Measurements of noise levels are made in accordance with CNS 8753(which is comparable to DIN 45365) in a sound proof chamber with a sound level Lp ＜ 15 dBA. 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.
‧The Parallel Operation
The volume air flow of two fans in parallel will be double in the free-air condition only. If the parallel fans are applied to the higher system resistances situation, the high system resistance that enclosure has, the less increase in flow results with parallel fan operation. Thus, this type of application is only recommended for the low system resistance situation - when the fans can operate near free delivery. The parallel operation is defined as using two or more fans side by side.
