The Collaborative International Dictionary of English v.0.48:

Loudness \Loud"ness\, n.
   The quality or state of being loud.
   [1913 Webster]

WordNet (r) 3.0 (2006):

loudness
    n 1: the magnitude of sound (usually in a specified direction);
         "the kids played their music at full volume" [syn:
         volume, loudness, intensity] [ant: softness]
    2: tasteless showiness [syn: flashiness, garishness,
       gaudiness, loudness, brashness, meretriciousness,
       tawdriness, glitz]