We were exploring the main room in the Tower Outta Nowheres, and we kept triggering a disembodied voice. Among the things it said were "Halt" and made the noise that other npcs make when you push past them. There wasn't a consistent trigger, but it did happen several times when we were near the table on the platform over the furnace.

We used Witcher senses, and the ghost lantern, and nothing.

Is this a bug?

Thanks.