The Power Mac G4 didn’t get the “windtunnel” nickname for nothing – its power supply is quite loud. Thankfully with the help of an adapter, a standard ATX (or SFX) power supply can replace it. I love putting “modern” power supplies into my retro machines to get less noise and clean power.
I went with a Corsair SF600 from my previously built Mini-ITX machine and it’s worked really well due to its small form factor. Although it’s rigged in place with two wire ties it’s not going anywhere. 😀