[yorwba]

Trees who suffer from drought apparently give off ultrasound when their dried cells are destroyed, but it seems to attract pests who then finish off the tree: https://www.thefreelibrary.com/Pop+chirp+bite+crunch+chew%3a...

[thomasfoster96]

But that's the sound of the tree decaying/dying, not communicating as the GP seemed to imply.