More volume inside the box allows the heat from the CPU out into that larger space, from where it then gets expelled out of the case. There are two gradients, CPU->Heatsink->Air_Inside and the Air_Inside->Air_Outside. The latter should be quieter if you can move the air more slowly, which should happen if there's more air volume inside the box to absorb the heat.

I agree with all I've read from others above. Low noise PSUs, CPU_Coolers and case fans all should help.

Where I differ from some is that I try to choose CPUs that are not so power hungry, e.g., the 'T' models and similar. Reduce the power dissipation within the CPU and you don't have to get so much out of the box. I'm also prepared to take a modest performance hit for lower dissipation, where others may not. That may be "just me" cool

Jazz relative beginner, starting at a much older age than was helpful.
AVL:MXE Linux; Windows 11
BIAB2025 Audiophile, a bunch of other software.
Kawai MP6, Ui24R, Focusrite Saffire Pro40 and Scarletts
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