the noise of ventilation fans

The noise of the ventilation fans including motor electromagnetic noise, mechanical noise and aerodynamic noise. Aerodynamic noise including the rotational noise and vortex noise in dB (decibels). Ventilation fans noise measurement commonly used sound level meter. Sound level meter is the instrument used to measure the size of the sound level by the microphone, impedance transformers, amplifiers, attenuators weighting network, meter circuit and power supply components.Rated voltage at rated frequency, the normal operation of the ventilation fans, the main performance parameters of the ventilation fans can be a graph, called a ventilator performance curve called the characteristic curve, usually ranging from free exhaust (exhaust airflow barrier-free) to (curve of the entire range of zero air flow).

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