Lichess kills sound on computer

I don't know if it's because I'm using Debian but it doesn't make the ding sound when a game starts or when I click the sound icon twice. Just wondering if I'm the only one with this.

I dunno if it was just me or what but it's fixed.

Sound problem fixed - many thanks

The sound the game starting is gone again but not the clicking of moving pieces.

I guess it's been fixed again. I dunno if it's just me.

It went away again.

It's back again. I really wonder if it's just me.

I don't know if it's because I'm on Debian but the sound has gone away yet again.

Then I restarted my Firefox browser and it worked again.

My sound also breaks down sometimes when I'm on this site. Usually this happens when I listen to music simultaneously. Initially, there is creaking, then the pulseaudio using a lot of CPU. Then the sound on the site disappears, but remains on the computer. Or sound may disappear everywhere, instead of sound noise will appear.
Helps me or restart the browser or command `pulseaudio -k` that kills that process.
I also use Debian 7.
I do not know whether the problem is on my side (debian, pulseaudio, iceweasel), or on the side of the site.