Noise characteristics
The linear sound power level for this fan is intermediate between an axial and centrifugal if all are selected for best efficiency and the same duty. The centrifugal generally has a falling noise spectrum with frequency, whilst the axial peaks in the octave band containing the blade passing frequency. A mixed flow fan has a noise spectra somewhat similar to the centrifugal except that there is a marked reduction in the 63 and 125 Hz bands making silencing more easy.
Posted in Fans Ventilation A Practical Guide