Why do cases and PSUs almost always have impractical cut-outs in the grille in front of fans for air passage? Whether this is due to indifference to an all-round honest product or ignorance of how inefficient a solution it is, remains a mystery. But we have devised a comparative test which refers to drawbacks of the hexagonal grille. Compared to the non-restrictive circular ones made of wires, the differences are significant.
Sound colour
| Type of obstacle | Dominant sound freq. and noise level, Noctua NF-A12x25 PWM@7 V | NF-F12 PWM | NF-A15 PWM | ||||
| Low range | Mid range | High range | |||||
| Frequency [Hz] | Noise level [dBu] | Frequency [Hz] | Noise level [dBu] | Frequency [Hz] | Noise level [dBu] | ||
| Hexagonal grille | Hexagonal grid | 126,992 | -77,806 | 339,028 | -69,128 | 1974,030 | -89,846 |
| Circular grille | 20,306 | -76,419 | 201,587 | -69,415 | 18780,243 | -90,922 | |
| Plastic dust filter | 126,992 | -68,642 | 339,028 | -74,269 | 5583,400 | -89,100 | |
| Nylon dust filter | Nylon dust filter | 195,849 | -63,331 | 201,587 | -62,790 | 1974,030 | -90,464 |
| No obstacle | Plastic dust filter | 130,713 | -77,289 | 339,028 | -74,287 | 1974,030 | -90,361 |
Was this tested with the grills on the intake, or on the exhaust?
And do you know how much of a difference it makes? Noctua with their NA-FG1 seems to mostly talk about intake noise.
Thanks for the question. Testing was done with a grille in front of the impeller. In a situation like this, the effect on the noise level is significantly greater. The increase is more significant than if it was the other way around (and the grille was placed behind the fan). This is why Noctua focuses on this kind of a situation. As part of HWCooling analyses, we are planning a detailed comparison in the future, where grilles with different structures will be in front of and behind different fans. However, this is not feasible in terms of time at the moment. But in the future, hopefully it will. 🙂