  In the frame of a four fermion interaction theory, we investigated the
collective excitation in light-heavy fermion pairing systems. When the two
species of fermions posses different masses and chemical potentials but keep
the same Fermi surface, we found that the sound velocity in superfluids and the
Meissner mass or inverse penetration depth in superconductors have the same
mass ratio dependence as the ratio of the transition temperature to the zero
temperature gap.
