Well I exported it again just to see if I could fix the noise. Did some reading and tried out a notch filter--reduced it by about half, but didn't get rid of it. I hear it much worse through the front of my speakers or through the mixing headphones. Gryph doesn't hear it at all... but the sound is just not right. The piano accompaniment seems to be worst culprit but also the sheer number of instruments playing makes a difference; when it's only bass and guitar there's no static at all, when the whole band kicks in for the chorus it's very noticeable.

I read oldmuso's thread about golden nuggets, and clicked the link to the big DAW... and there it was right in the description, "because the last thing you want to hear is your PC!" Oy.

So guys, here are my new questions.
1. if I throw this MP3 into a DAW, is there some way to remove the noise?
2. do you think the existing sound card created the noise?
3. if I get an audio interface, can I render an MP3 or WAV without noise?
4. this is totally counterintuitive to me, but could the rendering process be picking up the room fan? I wouldn't think an internal rendering would even be able to pick up anything in the room, but I have no idea if the microphone array is completely disabled even though BIAB says it is. But if it can't, could the fan blowing directly on me be vibrating my computer enough to interfere with rendering?

Honestly, I would have thought data and programming wouldn't be affected by external things like a fan, but I know enough to know that I really know very little about how things work!
Love is always worth the risk.

HP laptop; Windows 10 Home 64 bit; core i5; 2.40 Ghz; 8 GB RAM; 256 GB hard drive; BIAB 2021 Build 835.