²⁰The speed of sound through any substance is a function of both the substance’s density and its bulk modulus (i.e. the compressibility of a substance). Mathematically, c = where c is the sonic velocity, B is the bulk modulus, and ρ is the mass density. Water and air provide an excellent illustration of this principle: the speed of sound through water happens to be much faster than the speed of sound through air despite the vastly greater mass density of water, only because of the even greater disparity in bulk modulus between water and air.