I posted a question at another forum about "choked flow" where a fluid (in this case air) if flowing through a very small orifice. Apparently when the pressure difference on each side of a orifice is about 2:1 and above then the speed of the air passing through the orifice is limited to the speed of sound. This got me thinking...what is so special about the speed of sound? Please, I am a non physicist. I know that the speed of sound varies depending on the density of air and humidity, etc. but it is fairly constant. I also know that the speed of sound is much faster but fairly constant in water. Increasing the energy makes for louder sound but not faster sound. Why is the speed of sound fairly constant within the same medium? What keeps it from slowing down or speeding up significantly? What is the principal that limits sound to a fairly narrow speed?