The Red Goblin, as a fictional character, is not bound by the laws of science and can possess abilities or characteristics that are not possible in reality. If the Red Goblin is portrayed as being immune to fire and sound waves in a story or comic book, it is generally due to its unique nature or special powers.
In the context of fictional universes, characters often have superhuman or supernatural attributes that enable them to withstand or resist certain elements or forces. These attributes can include enhanced durability, heat resistance, energy absorption, or other abilities that provide protection against specific types of harm.
Therefore, if the Red Goblin is described as immune to fire and sound waves, it is most likely an aspect of the character's fictional abilities or traits. The specific explanation for this immunity would depend on the story or narrative in which the Red Goblin appears. It could be a result of genetic mutations, magical properties, advanced technology, or any other creative concept devised by the writers or creators of the character.