Siren Head is a tall guy with sirens on his head. He makes some siren sounds.

There is an SCP Sandbox article titled SCP-6789 (not anymore lmao) which is about Siren Head despite Siren Head being an independent character. In the article, Siren Head's sound kills people immediately. It is very poorly written.

For some reason people think that this is a real SCP and are very keen on sharing that belief in many comment sections. This is not the case. The confusion stems in part from a siren sound heard in Version 0.7 which is made in part from the sounds of a Chicago tornado alarm. A game about Siren Head also happened to use this sound. Thus, people began to believe that Siren Head was added or is coming to the game when in actuality, it isn't even an SCP.