The problem I see from the GitHub demo and the discussion here is that you zone out of the "background noise" and focus on the important/out-of-bound/etc sounds. Great, so why not just remove the background sounds and just alert the user to an urgent notification. There's nothing new to this, however, this is just audible notification alerts.
If you are going to run the sounds in the background, your brain is going to process out the on-going "normal" sound anyway.
Because the bet is that your brain is much superior at figuring out what is important/aberrant and what is normal as compared to the best algorithm you design.
E.g. if you know a co-worker is on holidays then a dearth of checkin sounds will seem normal (ideally this feeling of normalcy will be subconscious). On a different day, a dearth of checkin sounds might alert you that your startup isn't making much coding progress (depending on context not necessarily a bad thing!).
The problem I see from the GitHub demo and the discussion here is that you zone out of the "background noise" and focus on the important/out-of-bound/etc sounds. Great, so why not just remove the background sounds and just alert the user to an urgent notification. There's nothing new to this, however, this is just audible notification alerts.
If you are going to run the sounds in the background, your brain is going to process out the on-going "normal" sound anyway.