Depends on what you have in there.
Mechanical hdd do make a bit of noise, but ssds are completely silent.
Larger fans tend to make less noise than smaller ones and will usually be a lower pitch.
If you have an aio water cooler the pump can make noise, and depending on how its orientated you can sometimes get like a bubbly noise if there's some air moving around.
Can also get coil whine off power delivery parts. Usually gpus, but sometimes mother boards and power supplies can be whiney.
For the most part though desk tops are usually a lot quieter than a gaming laptop