Wave speed

Wave speed is a wave property, which may refer to absolute value of:
 * phase velocity, the velocity at which a wave phase propagates at a certain frequency
 * group velocity, the propagation velocity for the envelope of wave groups and often of wave energy, different from the phase velocity for dispersive waves
 * signal velocity, or information velocity, which is the velocity at which a wave carries information
 * front velocity, the velocity at which the first rise of a pulse above zero moves forward