[1] : The Collaborative International Dictionary of English v.0.48

loudness \loud"ness\, n.
   the quality or state of being loud.
   1913 webster

[2] : WordNet (r) 2.0

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

[3] : Moby Thesaurus II by Grady Ward, 1.0

60 moby thesaurus words for "loudness":
   amplitude, arsenic green, auditory effect, auditory phenomenon,
   blatancy, brazenness, clashing colors, coarseness, color clash,
   colorfulness, crassness, crudeness, crudity, dash, dazzle,
   dazzlingness, earthiness, extravagance, extravaganza,
   extravagation, flagrancy, flamboyance, flashiness, gaiety,
   garishness, gaudery, gaudiness, glare, glitter, gorgeousness,
   grossness, jaundiced yellow, jauntiness, jazziness, luridness,
   meretriciousness, noise, obscenity, obtrusiveness, panache, phone,
   rawness, ribaldry, roughness, rudeness, screaming color,
   sensationalism, shamelessness, shocking pink, showiness, sonance,
   sound, sound intensity level, sound propagation, sound wave,
   speech sound, sportiness, tawdriness, ultrasound, vulgarness

Loudness >> L Words
Loudness, definition of term: Loudness
loudness_pag1.html

Loudness Unit >> L Words
Loudness Unit, definition of term: Loudness Unit
loudness+unit_pag1.html