Similar question here, but my question is much more specific and the in-universe answers given can't really apply to Star Trek. I am asking about why the warp drive makes a sound in space - anyone who's seen the opening titles of TNG will fondly remember the 'warp' sound (which definitely adds to the program, but doesn't seem to be quite accurate). Is this explained anywhere in-universe (I'm thinking there may be some explanation come up with because of the warp field created?) in any sources?
When warp vessels are in pursuit, departing from a space station, or in any other way interacting with another warp-vessel on screen, and we hear someone on the bridge say "Captain, they're going into warp!", there is no accompanying sound from within the bridge. We never hear them go into warp when we're actually on a spaceship.
The only place where warp drives make a sound is in the area outside of the ships, and it is certainly possible that the 'sound' we hear is drowned out by a ship's own warp core, combined with shielding and hull protection that prevents us from hearing other ships move around in space.
But the simpler solution is that the sound simply does not exist, and is put there only to make it more exciting for us (unlike Star Wars sounds, which DO exist because pilots have audio feedback installed in their ships)
"Sound" as commonly defined does not travel through a vacuum. Period. However, it is conceivable that what we hear is not sound from the other ship's warp drive, but resonances in our own ship's hull caused by what the other ship does to local space. Energy certainly does travel through a vacuum, and the amount of energy expended by the now-long-gone ship has to go somewhere.
(unlikely this is mentioned anywhere, as it's the dull-and-boring bits they don't devote screen time to)