  Dielectric fluids experience a striction force in the presence of an external
electric field. Although the striction force on the entire body of the fluid is
usually zero, it does contribute to its deformations. In this paper, I show
that the speed of sound in dielectric fluids is reduced when they are exposed
to uniform electric fields of sufficiently high magnitude. Ferrofluids also
experience a similar striction force in presence of a magnetizing field.
However, their low relative permeability makes the effect very small.
