Élhendi said:
I suggest that you read the book.
Gandalf says the same in the film as in the book, although the setting is a bit different (there as well...)
I assume that the bit the OP is referring to is when
Boromir reaches out to take
the ring.
Elrond says "Boromir!" and then we hear a deep voice saying "Ash nazg durbatuluk, ash nazg gimbatul, ash nazg thrakatuluk, agh burzum-ishi krimpatul."
This voice is Gandalf's, but interwoven with Gandalf's voice is another voice, deeper, saying the same thing, but a second before Gandalf says it. I think this is Gandalf's voice, deepened even more by the computer and then put on an echo to make it sound scarier and more atmospheric.
In the moments after the ring is first put on the table a deep voice murmurs things that cannot be discerned. This, I believe, is also for effect. I don't know if it's the ring's voice (as it does have a sort of voice in the movie) or if it's just background to make it seem scarier.
Then later on in the scene, when everyone is arguing about who will go to
Mordor with the ring
Frodo starts to hear the
black speech again. And the whole of the council is reflected in the ring. The voice mounts in volume, drowning out the arguments of the council, and the council's reflection then bursts into flame.
This is, I believe, all in Frodo's head, perhaps an echo, or memory of what Gandalf had said, or the ring's power over him commanding him to stay with the ring, (or both) because as soon as he snaps out of it he says that he will take the ring.
I think PJ wanted to show that Frodo was being tormented/spoken to by the ring and that he almost didn't have a choice in whether or not he decided to go.
*shrugs*
So, Elhendi, yes, Gandalf does speak the verses that are written on the ring in the
council of Elrond, but I think the OP was asking more about these scenes when nobody appears to be speaking, yet an evil-sounding voice can be heard.
And to Dr. Thompson: The voice is saying "Ash nazg durbatulûk, ash nazg gimbatul, ash nazg thrakatulûk, agh burzum-ishi krimpatul."
Which translated means "
One ring to rule them all, one ring to find them, one ring to bring them all, and in the darkness bind them."
Does that answer things a bit?