The Collaborative International Dictionary of English v.0.48:
Vibrancy \Vi"bran*cy\, n. The state of being vibrant; resonance. [1913 Webster]WordNet (r) 3.0 (2006):
vibrancy n 1: having the character of a loud deep sound; the quality of being resonant [syn: plangency, resonance, reverberance, ringing, sonorousness, sonority, vibrancy]