Fan Noise Calculation

Sound pressure level and sound power level conversion: Free field: Lw = LP + 20lg(r) + 10.9dB Semi-free field: Lw = LP + 20lg(r) + 7.9dB Reverberant field: Lw = LP + 10lgV – 10lgT – 14dB Lw—Sound Power Level, dB; LP—Sound Pressure Level, dB; r—Distance from Measurement Point to Sound Source, m; V—Reverberation Chamber Volume, m; T—Reverberation Time, s. Calculation of Sound Source Superposition: When several different sound sources are superimposed:   ∑LP—The sum of the sound pressure levels LP1, LP2, LPn—represent the sound pressure levels (dB) of sound sources 1, 2, …, n, respectively. When M identical sound sources are superimposed: When two different sound pressure levels are superimposed, the superposition value can be obtained by looking up a table. That is, the difference between the two sound pressure levels is used to find the additional amount in the table and add it to the larger sound pressure level. Calculation of A-weighted sound level of the fan: LSA = LA – 10lg(QP2) + 19.8 dB (A) LSA—A-weighted sound level at the fan inlet or outlet, dB (A) LA—A-weighted sound level at the fan inlet or outlet, dB (A) Q—Airflow Volume at the operating condition point of the fan test, m³/min P—Total Pressure at the operating condition point of the fan test, Pa