Any idea what this sound is? Sometimes my MBP plays this somewhat distressing sound through its speakers (external if connected, otherwise internal, if my system volume is not muted).

Has anyone experienced this? What is it?

[Listen to the sound here.]

Things that make me doubt it has to do with the electrical system:


The fact this seems to be emanating from my system (affects either internal or external speakers)
The precise, musical, repeating nature of the sound
That it has occurred on battery power at my girlfriend’s as well as in my house (plugged in). 


Makes me wish there was an app like Little Snitch but for audio output instead of network traffic…
It’s the “Inactivity Sound,” called “Bass,” that Assistly plays by default when  you haven’t been using it for a few hours.

And I thought my computer was overheating!

I can’t understand why anyone would make a web app that non-obviously plays a repeating, scary sound on repeat hours after the user last interacted with it.  

Terrible.

Anyway, that’s one mystery solved.

You can +1 my relevant feedback to Assistly here.