To get some rough idea about relative noise levels of the fans, I performed some subjective analysis to the two 120mm fans I now had - Silverstone FM121 and Thermaltake 120mm UV fan.
As my currently only fan controller is still installed to the machine I write this on, I ran the TT fan just on 12V and 5V. The FM121 comes with control knob, so I put them side by side and adjusted the FM121 until their noise level sounded the same to me.
Other test setup parameters: I took power from ancient 120W ATX PSU, which comes with the fan. It is fairly quiet and I muffled it as well as I could, but still it was the noise floor in this test. I will later on mod old 12V battery recharger PSU brick to provide current without noise, but now I had to live with what I had in hand.
Listening tests were performed in our only windowless room at 4AM, so ambient noise was very low, sans the aforementioned PSU and distant hum of our home server (in neighboring room, in closet).
I also measured airflow with such a primitive way as holding a paper in front of the fans and examining which one could bend it more. To get repeatable results, I used several different papers and turned each or them 180 degrees and repeated the test.
At 12V TT is quiet but audible. 2 meters was not far enough to not hear it at all when being in direct sound path. Adjusted to similar noise level FM121 seemed to push a bit less air. Both were pleasent to listen to, mostly just whoosh of the airflow with some motor noise. As FM121 is rated for almost double the airflow and double the RPM at 12V, it had lower pitch and it sounded a bit rougher, like bigger engine running idle. TT had naturally the advantage of running at its nominal voltage, so it had smoother character.
When setting TT to 5V and trying to match same noise level with FM121, I found both of them to be very quiet. In these test conditions at 50cm away in direct soundpath their noise ceased to be heard (remember the ambient noise). It was impossible to set both to exactly the same noise level so all the comparison at this voltage is even less accurate than the rest.
At this voltage TT had some irregularities in sound; it started ok at 5V, but now and then there either was or was not some resonance-like additional noise. However, that noise was so quiet that it’s hard to count it as a defect - I could hear it only from some 20-30cm distance. The FM121 had a bit more pleasant motor noise, mostly due to lower frequency and it also felt like it was moving a bit more air.
All in all, both fans sounded, looked and felt like quality workmanship. When soft-mounted and enclosed inside good computer case, the TT fan should be either entirely inaudible or barely audible depending on your other components and noise floor. At 5V it definitely is inaudible it not in direct soundpath.
Silverstone FM121 performs also very well considering that it is rated for whopping 120CFM at 12V. It undervolts nicely and at all speeds it has pleasant sound and good airflow per noise ratio. At full speed it’s of course nowhere near silent, but the noise is mostly just pleasant whoosh and it moves *a lot* of air. It looks and sounds like a very good compromise between wide operating range and noise.
I will return to this subject when I have time to disassemble some 80mm fans from my primary computer and set up closed loop for the Laing Delphi pump. Then I can hopefully say something more than “wow, they are nice fans”, since I can compare them to some fans with known noise level.
I will also test all the samples against each other when I get to that point, so I can give you some idea about sample variety. I will have three of both fans, which should be enough to count out some uncertainty, altough the all TT fans are from the same batch.