Can incorporeal creatures speak?

Question

I got to thinking about how exactly incorporeal creatures interact with the corporeal world and I wasn't exactly coming up with anything that explicitly stated whether they could communicate or not. Like, sure, maybe they can speak to other incorporeal creatures, but what about using an incorporeal creature or spell to send a message to a corporeal one? Would that be possible?

It seems like they can't really interact physically with the corporeal world, and can be heard moving if they want to be heard, but... nothing says anything about talking, and I'm now very curious as to whether there's an answer to this.

Answer 1

Mechanically

Neither the Incorporeal subtype nor the Incorporeal (Ex) trait prevent a creature from talking. This doesn't necessarily mean that they can, but some creatures indicate they cannot speak, while some incorporeal creatures do not indicate this.

Story-Wise

Any one GM can decide whether an incorporeal creature has the necessary interaction with the environment/air to communicate. However, Paizo has given situations where incorporeal creatures have spoken in their Adventure Paths; as well, they have indicated that some spirits (notably Poltergeist, which come back from destruction) could come back as a Rapping Spirit, and suggest this as a means of communication outside of speech such as in

Ruins of Azlant, book 1

Additionally, there is an entire Story feat about communicating to the undead that lists simple interaction with them as a time the feat is functional. It is clear, to me, this isn't written out explicitly because it is intended to be changed based on circumstances.