I changed the internal fans by others with less noise, and added an extra fan over the motherboard. This improvement need to print a 40x40 support to replace the internal turbine.
Photos, links to 24V silent fans and stl at Sovol SV04 motherboard fan modifications by Lombar - Thingiverse
In the extruders I replaced the noisy turbines 4020 by the 5015. I designed an adapter and the ducts for this turbines. Included with the STL files there is a video comparing the noise of the fans installed. The ducts are based in the original ones and share the shape of the output.
The difference is so many dB less