It depends on how empty you mean by empty. In a pure vacuum there’s no sound. Some black holes and star systems have enough gases around them that what might visibly look “empty” between the star and surrounding planets isn’t really empty. There, sound travels out in massive waves. Luckily our solar system lacks enough matter to transmit sound from our sun to our planet because it would be really frickin loud all the time if it did. Also, gravitational waves expand and compress space (and the matter within it) not too dissimilar from how sound travels through matter, but unlike audible sound waves, gravitational waves don’t require a physical medium. But this is how we can hear black holes. Also, they travel at the speed of light if I remember correctly.