The load on CPU causing the noise is EMI. It’s a very common issue with onboard sound. Many people use USB soundcards to help with this.
The 100% CPU usage that you’re reporting with EVE is something we’re investigating. We’ve not been able to reproduce it in house yet. I’m speaking to a number of people in the community who are experiencing it to try and reproduce it. I’d ask you to file a bug report so we can get your system info, as this issue seems to be very user specific. Feel free to tag me in it if you do.