### Strutt Help

Empirical Fan Noise Prediction    1/1

Strutt|Input Data|Empirical|Fan inserts sound power levels into the active row of the worksheet.

The total sound power has been calculated using the formula:

L_W = 20log_10 P + 10log_10 V + 40

Where,
P is the fan total static pressure, Pa
V is the fan volume, m3/s

Octave band sound power levels have then been calculated by adding spectral corrections as follows:

 Fan Type 63 Hz 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz Axial -5 -5 -6 -7 -8 -10 -13 FC Centrifugal -2 -7 -12 -17 -22 -27 -31 BC Centrifugal -7 -8 -7 -12 -17 -22 -27 Propeller 0 -1 +2 -5 -9 -10 -17 Mixed Flow -12 -11 -10 -10 -13 -17 -22

Blade-pass frequency is calculated is calculated as: BPF = (rpm*number of impeller blades)/60. With this option selected, 5 dB is added to the octave band containing the BPF and 3 dB is added to the octave band containing first harmonic.

References:

• ASHRAE Handbook, p47.4
• Arup Sound and Vibration in Mechanical Services Design, p36