I’m on Alpha Periphery C2 at coordinates 99 North , 66 East , 1,332 above, bearing: 209 degrees. I’ve been exploring quite a way out but recently returned close to the portal. I haven’t encountered this at all while scanning until now, but there’s a sound in the middle quite a bit more sharp and shrill, like a tweeting bird. Is this a bug or is it really that the terrain there is that varied?

Wow! This is an original alpha seed. Beta seeds are in an eight-character format now.

Anyway, I’ve finally found a moment to look into this. This is intentional. You’re facing the portal that you exited to get here. It’s about 85 meters above you from this location. It sounds a bit louder because structures have a brighter sound than the surrounding terrain. Ideally this helps teterhedra, portals, etc. stand out against varied terrain like this.

I’m wrapping up the new update to release within the next week. It will include some mixing adjustments to cues like these.