Blade length is always the “topic”, but will be more common with 140mm fans than smaller variants. Some bet on long blades for preference of selected features, the other manufacturer on short ones. And such (short) and overall more robust blades are also used by the 140mm Aorus fan. From certain points of view this is quite a big advantage, but for which something had to be sacrificed. It’s a quid pro quo.
Base 6 equal noise levels…
There are several options by which to normalize the test modes for fans. In the previous chapter, we wrote that perhaps the least appropriate option is equal speed.
Settings according to the same static pressure or flow are for consideration, but we find it most sensible in the long term to normalize the measurement modes according to the same noise levels. Firstly because decibels are a logarithmic unit and all others scale linearly, but mainly because you can orientate fastest by the same noise levels. The easiest way to compare the efficiency of fans is just by how they perform at the same sound pressure level. Of all the options, this is the one that most people can best imagine and bounce off of when considering other variables.
The individual noise level modes are adjusted from low levels continuously to higher levels. All users will find their results in the tests, regardless of whether they prefer very quiet operation at the limit of audibility or whether high performance is paramount.
The quietest mode corresponds to 31 dBA, followed by 33 dBA, and for each additional mode we add 3 dBA, which always doubles the noise level (36, 39, 42 and 45 dBA). Finally, we measure the fans at maximum power. Here, each one already has a slightly different noise level, which we also report. If there are missing measurements between the results for any of the fans, this means that it was not possible to set the target noise level. Either because its minimum speed exceeds the quietest mode of 31 dBA or vice versa because the fan is quieter than 45 dBA at maximum power.
It is important to add that our noise level measurements are incomparable to the values quoted by the fan manufacturers in their specifications. One of the reasons is because we use a parabola-shaped collar around the sensor of the noise meter, which increases sensitivity. This is important in order to distinguish and set to the same noise level even modes at very low speeds, especially 31 dBA.
The noise meter next to the fan is quite close for sufficient resolution. The distance between the frame and the sensor is 15 centimeters. The sensor is positioned in such a way that there is no distortion or that the noise level measurements are not affected by airflow. Therefore, the noise meter is centered perpendicularly to the frame that defines the depth of the fan. Everything is always at the same angle and at the same distance. We use an inclinometer and markers to set the distances precisely and always the same.
We use a Reed R8080 noise meter to measure noise levels. This allows real-time averaging of samples, which is important for fine-tuning individual modes. We tune the fans until the specified noise level is reached to two decimal places, for example 31.50 dBA. The noise meter is the only instrument we calibrate inside our testlab. The other instruments have been calibrated by the relevant technical institutes. However, in the case of the noise meter, calibration is required before each test and we therefore have our own calibrator. This is already calibrated externally according to the standard.
Nice to see the 140mm fan reviews rolling!
Also, would it be possible to publish noise samples for your fan/cooler reviews? Preferably for all scenarios where you perform frequency analysis?
And they will continue to come, tests of 140 mm fans. But we probably won’t exaggerate it, so that they stay in a relevant ratio (according to the interest in whichever format in general) to 120 mm models.
Which noise samples do you mean? From spectrographs? Do you want that data for your own purposes, for your own analysis? If so, we can send you the noise levels at all frequencies in all tested scenarios almost immediately (e.g. by e-mail). We can certainly post them on the web somewhere, but it will take more time, as we will need to create a section for this somewhere. Making it make sense on the web will be more time-consuming and at the moment we are quite overloaded and it is hard to find space for extra activities. :/
Always looking forward to your fan reviews regardless of size!
For noise samples, I mean audio files so I can listen to them to make a subjective judgement. In reviews you often mention the differences in frequencies between obstacles/fan models etc. With audio files to listen to, it will be much more easy to understand the difference.
Maybe you can consider compiling the audio files for each fan and upload to YouTube as a video, for example, which perhaps take relatively little effort, though I am not sure if the audio quality is satisfactory. Anyway, it is only a suggestion so please decide on whether you think it is worth the effort or not.
I understand now, and I am also sorry that I am now likely to disappoint you.
Sound recordings are something I boycott against and the goal is to get more and more people to learn to read spectrograms. Sure, it’s more complicated, but we plan to publish materials to facilitate reading these charts. We will select a few fans that have the biggest differences in the frequency characteristic of the sound, make a sound recording of them, and put a spectrogram against it. On it we then explain which component of the sound represents what in the spectral analysis.
You know, I’m willing to sacrifice all my time for these things, but I have to see some meaning behind the results. And sound recordings don’t make sense to me because they can be extremely misleading. While the user thinks he’s hearing the fan, the sound system with the speaker on top is laughing at how they have been perfectly fooled. It is certainly not necessary to elaborate that the same recording sounds different on each speaker (it is determined by the frequency characteristics of the sound equipment of the end user), and this also with regard to the volume that the person sets. To judge something on the basis of the sound recording is therefore very inaccurate and misleading. I would probably suffer a lot when making them with my high demands on the relevance of things and at the same time it would reduce the relevance of spectrogram, which everyone sees the same way.
I believe that after this message you will not give up on our tests and sooner or later you will surely find out (also with the help of various auxiliary materials, which we plan to publish on this topic), that you understand everything perfectly also with the help of spectrograms. 🙂
Not disappointed at all, very satisfied with your answer. Looking forward to the articles explaining spectrograms, I’ll admit I never really understood how to interpret them.