The audio quality for notifications and phone calls is horrible on my 1020 if at high volume. Very crackly. Naturally, if I lower the volume to the point that the notification and phone call audio isn't crackling, they're both relatively useless at that point. This is just plain phone audio. Not bluetooth/headset audio.
Music sounds just as fine as it always has on 8.1, so it's not a general audio issue. So, in the case of the notification sounds (that seem universal with Windows 10 across devices), I feel like that's got to be something about the audio files being used. Not sure why the audio quality in phone calls is so bad (imo, it was never great on a 1020 to begin with). It almost feels like I'm on an underpowered desktop PC that uses integrated sound while its CPU usage is at max, in terms of how the audio quality of notifications and voice calls seems to operate in a similar poor fashion. No idea if that's what the cause is-just prognosticating.
Also, I had to switch out the phone app for the new phone app. The old one didn't do a thing on 10136.