In my case pavucontrol makes the problem disappear only temporary (and so does the KDE settings application). After a minute or so the buzzing sound returns. Seems to be some periodic background task that triggers it again.
Currently I use linux-lts which is 4.14.x at the moment to avoid the issue. However this problem will become a showstopper once linux-lts is updated to something >= 4.15.
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