I actually saw this video some time ago. I have to disagree with you on few points.
You have an open bench situation - you don't have a case. The case changes the acoustics of a fan. It can sometimes make a fan config. more bearable or sometimes it can cause resonance - which is pretty annoying sound even if it is quite low.
Those Noctua fans have very similar noise profile to the TY-147A fans. As doyll posted pictures before with them side to side - apart from the colors and the small ridges on the Noctua - you can't really tell them apart. Also, the TY-147As in my configuration sound similar, with the exception of the "pulsing" effect which I believe is maybe a microphone phenomenon.
I will copy-paste something from my previous post so you don't have to search for it.Warning: Spoiler! (Click to show)
Now the TY when ramped up sounds a bit like the proper of an airplane. The XF however - reminds me of a hornet. The TY noise dies quicker with distance, while the low treble of the XF does survive distance and it is pretty hard to dampen by the case. To my ear - a single XF at 700 RPM is twice as loud as dual TY-147s at 800 RPM. Also, having 1 TY or 2 TY did impact noise rather little. While having 2 XF did substantially increase the noise over a single fan config.
This are my notes on the single fan config of the noise profile. I did the test at 3 AM when there is no almost no noise. I live in a place where cars and vehicles are not allowed in a perimeter of more than a 100 meters. So with the exception of a drunk student passing by - the noise level is amazingly low.
RPM TY-147 Noise
278 Quieter than system
490 Same as rest of the system
672 Barely audiable over system - airflow noise - 10 cm
806 Barely audiable over system - airflow noise - 30 cm
981 Medium aiflow noise and slight humming noise - 50cm
1244 Loud humming noise
RPM XF-140 Noise
755 Barely audiable airflow noise - 50 cm
1123 Medium-Loud turbulence noise - 50 cm
1285 Loud turbulence noise - 50 cm
1436 Even louder Louder
As I said before, the case does a pretty good job at "silencing" or better said - "absorbing" the noise. I got an old HAF 912+ done with proper steel. Not like the flimsy Corsair R300, T230, T600 and etc. bendy cases. It absorbs a ton of noise that is produced by the TYs. I can hear a very large difference if the TY is running in a closed case or out in the open.
The XF however, keeps its sound profile regardless of it being in a case or not with minimal loss. The turbulence noise combined with a the treble survives the case and distance very well. The XF fan noise is very similar at 30 cm, 50 cm and 1 meter. The TY noise dies rapidly after 30-50 cm.
Also you said "to most of us they sound way better and less loud", but I completely disagree. Humans are programmed to be more sensitive to trebling noises. Because we were supposed to run away from lions and tigers and wolfs and stuff. And when one of them roars - you get the adrenaline rush.
To me the XF sounds like a hornet. And the TY/Noctua - like an airplane propeller. One is certainly more unpleasant than the other. Heavy turbulent sound makes me restless.
But this is the personal part that you can't just measure on a dB(A) scale. Good work on the video, btw. Very nicely done and provides a very good illustration. Keep up the good work!