If the N9 is lagging or seems a bit sluggish the audio quality then degrades or becomes slightly distorted. I've noticed it while streaming over bluetooth. At first the quality is great, then after playing with the N9 a bit while it's streaming, it lags a bit and seems sluggish and the audio stutters. When it stops stuttering, the phone returns to being smooth but now the audio quality seems degraded. It doesn't return to normal unless I disconnect bluetooth, shut the music app and then redo the process over again. (It has nothing to do with the quality of the song file because quality is superb if phone is running smoothly.) Maybe one or two apps are open during streaming (music app, email and messages) so nothing intensive.
Also noticed this with headphones of any kind.

Anyone else notice this?

Yup, I noticed this also sometimes but I kept thinking that its just me, so often times I just ignore it, glad to know im not alone :-P. I Get this when I listen to music for a very long time, I mainly use this phone as a media player.

Another nice find mate, sounds totally lodge-able to me:
http://harmattan-bugs.nokia.com/
Once you do, post the bug url here, so others can subscribe & vote.

Bug submitted. Please vote for it here:
http://harmattan-bugs.nokia.com/show_bug.cgi?id=560

well done, thanks for that.

I am also experiencing bluetooth audio connection problems with somewhat older, but premium Nokia wireless devices BH-503 and MD-7W. They are influenced by WiFi behaviour and any other activity on the phone. Especially typing on the standard keyboard with word suggestion on. Furthermore it seems also very prone for obstruction of the visual path between phone and peripheral: there will be an audio hiccup when someone walks between the phone and the peripheral in case they are only some three meter apart.

Harmattan bug 125 (https://harmattan-bugs.nokia.com/show_bug.cgi?id=125) concers this issue. If you care to search the internet on 'N9 bluetooth audio problem', or something like that, you get quite some results. Especially for the Nokia Support site. So the problem is well known.

Witnessing the replies from Nokia devs, they do not seem to be able or willing to solve the issue however. Wireless listening to music while performing other tasks being a basic use case for a smartphone, I think this is unacceptable.
How can we gain momentum to have this issue solved?

Ah I recall this one, I am subscribed to it...
I've tried to get them to compromise on this one, so far they've been non-responsive
Perhaps it's best to suggest that the new one, be merged into this.
Although it's described slightly differently, it's possibly fundamentally the same.
Then again it's prolly best to flesh-it-out with Nokia devs 1st, & let them be the judge.

I saw the bug you're talking about when searching before I submitted this bug. I think they are different problems. The bug you mention deals with interference, while the bug I mention seems to be a software related problem as well as the issue I mention doesn't only pertain to bluetooth but it extends to using it with a wired headset. The problem occurs more frequently during bluetooth audio streaming which is slightly intensive on devices and causes a slow-down or a sluggish feeling when using the N9 during this operation. However, it's not always sluggish but when it is and even when it resolves itself the problem is created and the audio quality is degraded as a result there-on-after unti you close the music app and restart it. As I said this is not limited to bluetooth, it also occurs, however less frequently, with using a wired headset. Seems it has to do with the way the phone handles intense usage and processes.

Come on guys please vote for this. The problem occurred yet again today while playing music through my car. Like I said, it's not limited to bluetooth but also occurs (less frequently) by playing music via wired headphones. I use only my N9 now for media (why carry more than I need?) and this really makes it difficult. I think the problem lies with how the N9 deals with tasks while playing music and its effect on pulseaudio during intensive tasks. I think it happened when my N9 was updating my two email accounts. But seriously it is noticeable. While you are listening to music, randomly the sound begins to suck.

Another community member from the Meego Forums provided some insight on the issue.

http://forum.meego.com/showthread.php?t=5465

Can anyone here confirm this as well? Would love to get this bug squashed.