Facebook is building an audio chat product that is similar to popular young app Clubhouse, according to two people with knowledge of the matter, as the social network aims to expand into new forms of communication. Clubhouse, a social networking app, has gained buzz for letting people gather in audio chat rooms to talk about various topics. Mark Zuckerberg, Facebook’s chief executive, has been interested in audio communication forms, said the people with knowledge of the matter, and he appeared in the Clubhouse app Sunday to chat about augmented and virtual reality. Facebook executives have ordered employees to create a similar product, said the people, who were not authorised to speak publicly. The product is in its earliest stages of development, they said, and the project’s code name could change.