How do we know that sound signals recorded aren’t just from the release of biomolecules? Using the nervous system to produce sound is a more intentional process than the release of biomolecules for chemical signaling, which is something even simple multicellular organism do
I can absolutely confirm that neither cats nor dogs particularly enjoy hearing multiple frequencies in that range, as I use ultrasonic noisemakers to train dogs and cats. Both species have had specific individuals that reacted as though I had just beaten them, and all the individuals of both species reacted in such a way that it was clear that they would do just about anything to never hear those noises again.
That being said, I wonder if they could hear that frequency all the time and were freaked out that a human was shouting in plant language.
The unpleasant reaction could be to the shape of the sound rather than just the frequency. Like a sin wave isn't a pleasant sound, though it's not bad at lower amplitudes.
Right, but what’s the source of the sound? If it’s not intentionally produced, but rather a chemical reaction or reaction byproduct, then it says something different about plant communication
The sounds produced by plants aren't used for communication, at least as far as I've understood it. They are, as you say, just sounds produced as part of other processes. They aren't talking any more than a tree talks when in creaks in the wind.