Noise Calculation Method Of Computer Fan

The noise of Computer fan mainly comes from air noise and mechanical noise. Air noise is generated by the friction and compression between the fan and the air during rotation; The mechanical noise is caused by the internal mechanical movement of the Computer fan, such as motor vibration, bearing friction, etc. The calculation of mechanical noise is generally related to the fan structure, materials and manufacturing process.
The noise level of Computer fan is usually expressed in decibels (dB). The decibel is a logarithmic unit used to calculate sound intensity, which is a weighted calculation based on the sensitivity of the human ear to different frequencies of sound, which is more in line with human auditory perception.
The noise calculation of a single fan usually involves the following main parameters:
The sound power level (Lw) of the fan: represents the total sound power generated by the fan, in dB (A).
Distance (r): The distance from the observation point to the fan, usually measured in meters (m).
Sound power level distance index (n): used to describe the fan attenuation with Distance decay.
Based on these parameters, the noise level (Lp) of a single fan at the observation point can be calculated using the following formula:
Lp=Lw -20 * log10 (r) - n
When multiple fans are working simultaneously, their noise will generate mutual noise, and the noise effect needs to be considered accordingly.
For fans operating in the same phase (i.e. with the same frequency and a phase difference of 0), their sound power levels can be added together. Assuming that the sound power levels of two fans are Lw1 and Lw2, then their combined sound power levels Lw_ Total can be expressed as:
L_ Total=10 * log10 (10 ^ (Lw1/10)+10 ^ (Lw2/10))
Similarly, if there are four fans with noise levels of Lw1, Lw2, Lw3, and Lw4, then their total noise level is:
Logarithmic addition: L_ Total=10 * log10 (10 ^ (Lw1/10)+10 ^ (Lw2/10)+10 ^ (Lw3/10)+10 ^ (Lw4/10))
For fans operating in different phases (i.e. with the same frequency but no phase difference of 0), the synthesized sound power level needs to consider the maximum impact of phase difference on noise, and the calculation complexity is relatively high.
Please note that the above formula assumes that the noise of each fan is independent of each other, that is, they do not affect each other.
Additionally, these formulas can only calculate the sum of noise levels and cannot describe the subjective perception of noise. In practical situations, people may feel that the noise generated by multiple fans is much greater than that of a single fan, which is related to human auditory perception. Therefore, in practical applications, other factors need to be considered, such as the frequency characteristics, spatial distribution, and human auditory characteristics of noise.