Sound pressure level and sound power level conversion
Free sound field: Lw=LP+20lg(r)+10.9dB
Semi-free sound field: Lw=LP+20lg(r)+7.9dB
Reverberant sound field: Lw=LP+10lgV-10lgT-14dB
Lw-Sound power level, dB
LP-Sound Pressure Level, dB
r-distance of the measurement point from the sound source, m
V-volume of reverberation room, m
T-reverberation time, s
Calculation of source iteration
When several different sound sources are iterated:
∑LP - sum of individual sound pressure level iterations
LP1, LP2, LPn - sound pressure level of sound source 1, 2, ..., n, respectively, dB
when M identical sound sources are iterated:
When two different sound pressure level iterative, its iterative value can be obtained by looking up the table, that is, with the difference between the two sound pressure level, look up the table to get the additional amount, added to the large value of the sound pressure level.
Calculation of fan specific A sound level
LSA=LA -10lg(QP2)+19.8, dB (A)
LSA - fan air inlet or outlet specific A sound level, dB (A)
LA-Fan air inlet or outlet A sound level, dB (A)
Q-fan test working point air volume, m 3/min
P-Fan test working condition point full pressure, Pa
| Ventilator type | Specific A sound level LSA (dB) | measuring position |
|---|---|---|
| Forward Blade Centrifugal Ventilators | ≤24 | – |
| Backward facing plate blade centrifugal ventilators | ≤27 | – |
| Wing-shaped blade centrifugal ventilators | ≤22 | According to GB/T 2888 |
| Radial Blade Centrifugal Ventilator | ≤22 | According to GB/T 2888 |
| Axial flow ventilator | ≤35 | – |
