I figured he was just kiding around, but I suppose he's 'technically' correct, by the definition given. 300 kps is pretty darn fast, tho; sound thru something like iron is around 5 times faster than sound thru air (iirc), which is around 300 mps (iirc).
Anyhoo...
If you're talking about external sounds, I'd go for a quiet whooshing sound, getting louder as you have to go faster thru the air. The sound of the air will get louder as you go faster of course; imagine being in a quiet car and listening to the air sounds. Rolling down the windows messes it up, but you might be able to make do by rolling them down all the way, and not driving too fast.
Inside, the sound of air conditioning. Air is CONSTANTLY blowing thru metal ductwork, so you could probably go to the furnace room of a building to get an idea, or most houses have central heat and air that's loud enough. I would imagine a luxury ship would dampen this sound some.
Engine sounds.... well, reactionless drives kind of vibrate you to your core without letting you actually hear anything. That's the reason starports don't let people wander out into the fields when ships are operating, and why ships don't land directly in berth-slots; they're towed to and from their berths and the landing zone. Reproducing that over speakers is nigh impossible, and probably as unpleasant for the viewers as smell-o-vision would be (but in a different way).