So, you're saying sound has a spiritual air about it and an empty-headed medium is a sound trap? :-?However, sound will travel at different speeds depending on the medium it is passing through. Due to this, the "Mach" number is based on the speed of sound in a vacuum.8-)
Off topic but I just had a call on my cell phone. He said "Hello is 'H' there" So I said 'yes, H is there because he is not here'. It was a very odd wrong number..

(It's true, not a joke.)