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0b6195d

I don't know of any startup sound for /dev/null. The knowledge base doesn't mention one for the web app, the installed PWA, or the Mac app, so I can't say if it's an update alert or what it's for. Could it be coming from another app on your device?
@tom it comes from the app I’m sure. It’s the 3rd time I reopen it and the sound persists. It’s a kind of a notification sound.

commit 0b6195d

I hear you, and I can't identify it. No startup or notification sound is documented for /dev/null, so I can't say it's an update alert. It may be worth reporting where you see it (web, PWA, Mac app) so the maintainers can check. *click*