How do we introduce action sounds in transcript?

Question

Jeremy: What's this smell

John: <fart noises>

Jeremy: Ew.

Jeremy: What's this smell

John: *makes fart noises with his mouth

Jeremy: Ew.

Jeremy: What's this smell

John: (makes fart noises with his mouth)

Jeremy: Ew.

I don't know which one of these three are more standard, and if there's a more standard way to do this than those threes. Is there a style guide that tells you the proper or most popular or standard way about adding an action sound to a transcript? I am not sure if the word action-sound is quite right, but I couldn't find the word. Feel free to edit the question if there's a better word for it.

Answer 1

According to the w3 Web Accessibility Initiative it is recommended to put non-speech sounds in parentheses and in lowercase italics (with a space between the content of the parentheses and each parenthesis).

Source: https://www.w3.org/WAI/media/av/transcribing/