Is the sound in high speed camera videos real?

I keep wondering when watching YT videos of people doing high frame rate recordings whether the slowed down sound in some of them is real (the ones that have sound).

Take for example this one where they use a Phantom camera not a Cronos one. https://youtu.be/Dy55X4QaAAU?t=395

On another channel (Beyond the press) https://www.youtube.com/channel/UCveB47lgzZJ1WOf4XYVJNBw I have noticed that when they use different cameras, some footage does have slowed down sound.

Of course this could all be clever post production sound effects but I doubt that these channels can actually make it sound so convincing.

So my question is: Can the Phantom record sound in sync with the video and does it sound as amazing as the video looks?