Source : Webster's Revised Unabridged Dictionary (1913)

Vibrancy \Vi"bran*cy\, n.
   The state of being vibrant; resonance.

Source : WordNet®

vibrancy
     n : having the character of a loud deep sound; the quality of
         being resonant [syn: {plangency}, {resonance}, {reverberance},
          {ringing}, {sonorousness}, {sonority}]