where is the density (mass per unit volume) of air, is the speed of sound propagation, is ambient air pressure, and is the adiabatic gas constant for air (ratio of the specific heat of air at constant pressure to that at constant volume)
where is the cross-sectional area of the tube section. Note that volume velocity is in units of meters cubed per second.
where and are the inductance and capacitance, respectively, per unit length along the transmission line
where and are the permeability and permittivity, respectively, of the vacuum
It is odd and interesting that waves in the vacuum are subject to the special theory of relativity (speed of light always measured to be the same, irrespective of one's velocity)