The Collaborative International Dictionary of English v.0.48:

Audible \Au"di*ble\, a. [LL. audibilis, fr. L. audire, auditum,
   to hear: cf. Gr. ? ear, L. auris, and E. ear.]
   Capable of being heard; loud enough to be heard; actually
   heard; as, an audible voice or whisper.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Audible \Au"di*ble\, n.
   That which may be heard. [Obs.]
   [1913 Webster]

         Visibles are swiftlier carried to the sense than
         audibles.                                --Bacon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

audible
    adj 1: heard or perceptible by the ear; "he spoke in an audible
           whisper" [syn: audible, hearable] [ant: inaudible,
           unhearable]
    n 1: a football play is changed orally after both teams have
         assumed their positions at the line of scrimmage

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "audible":
   acoustic, articulate, audile, audio, auditory, aural, auricular,
   clear, contrastive, definite, distinct, distinctive, hearable,
   hearing, hi-fi, high-fidelity, otic, otological, otopathic,
   otoscopic, phonic, plain