Ringing a bell near my villager trading hall causes the farmers, clerics, and one librarian to freeze, meaning they stop moving, working, restocking, sleeping etc. They also stop showing their items/emeralds when standing near them with something they can trade. All they seem to do is turn around occasionally. They stay like this until the world is reloaded, at which point they return to normal until a bell is rung again.

There are other villagers; masons and librarians, that seem unaffected by the bell and respond to it by panicking as they should.