So since a few days, I irregularily get a bell-type sound from Firefox. I know it’s from Firefox because I spent an hour or so watching pavucontrol to find out which application was responsible for that sound (It was CubeAudioUtils or something similar with the Firefox logo).
I first suspected it was a monitoring application, but muting that tab does not have any effect on the sound. It still occurs irregularly.
I need to find out which tab is responsible for that irregular, rare (maybe once per half an hour, maybe more rare) and short (maybe a second or two) sound. Due to these properties, checking which tabs shows the speaker icon while the sound is playing is not a viable option. Closing all tabs is also not an option, not only because I need those tabs, but also because it may occur again in the future (I assume it is some kind of web application I use), and then I am no wiser about the cause.
Also not an option are addons which block audio from playing at all or forcing click-to-play everywhere.
How can I do this?
This is on Debian unstable with Firefox 45.6.0.
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