The purring sound of the Enterprise warp core is iconic (for example https://news.avclub.com/read-this-behind-the-scenes-of-sci-fi-s-most-soothing-1798247701). Is there an in-universe explanation for the components or processes specifically responsible for this sound?
I'm asking specifically about the throbbing of the warp core, not the engines.
This YouTube video lets you hear the throbbing sound well:.
It's interesting that some "ambient" videos on YouTube don't present the throbbing sound as distinctly. Which makes me wonder why the film makers sometimes included it and sometimes didn't. Either it's accidental, or the throb is present sometimes but not others for a reason. I'm wondering what that reason might be.
It's possible the throbbing sound has nothing to do with the warp core and is due to some other part of the engine room. But in scenes where the rings of light surrounding the core flash in a way to emulate motion, the flashing seems to follow the same period as the throbbing sound.
This video shows the synchrony between the flashing tubes and the throbbing sound (although the throb sound is very subtle):