Ape Apps

I was definitely the game, going to home screen stopped the noise. Going back into the game, it started again.

Not sure if this is a bug, or what. But I just just started playing, and I was trying to build the helium extractor. When suddenly, the game started making a high-pitched beeping sound.
I'm not sure if it's supposed to do this, but I was given no notification, indicating a warning of some sort. So I have no idea the origin of the sound.
If it's and alert of some sort, what is it for and how do I stop it. If it's not supposed to happen, please move this thread to bug reports.

Thank you for your time.