Case fans are always on, however, if they are modulated, they should spin at lower rpm under light loads and ramp up as components are stressed. The noise is most likely the result of the Dell industrial grade server fans . . . so consider upgrading your fans to better quality, more quiet fans that are compatible with the XPS 8950.
Recently bought an XPS 8950 (i9-12900K, 32GB DDR5, CPU liquid cooling) and was surprised to find that the main large fan is always on, from the start, no matter what software is running. The case makes a sound like an engine - around 45db+ measured from 60cm away. Surely the main fan should only kick in when the processor is under load? Constant 45db engine sound is loud. Is the constant fan a fault, or is this usual? Thank you.
XPS 8950, is your main fan always on?