Several times the speed of sound? That is meaningless when there is no media for the sound waves.
I think a better unit might be furlongs per fortnight.
> 2.43 kilometers a second, or 1.51 miles a second, or 5,400 miles an hour, or 8,700 kilometers an hour.
> There is, of course, no air and no sound on the Moon, so a "Mach number" doesn't really make sense. But if there were air, the speed would be about Mach 7, seven times the speed of sound.
I still call it sound when I hear things under water. Gas isn't special.
When someone knocks on your door, you still say you heard the sound, even though the pressure wave was transmitted through the solid door material (before then being transmised to the gas in the room). Likewise, we still file a noise complaint when the neighbor is throwing a raging party, even though we are feeling the bass as much as we are hearing it.