Source : Webster's Revised Unabridged Dictionary (1913)

Acoustic \A*cous"tic\ (#; 277), a. [F. acoustique, Gr. ?
   relating to hearing, fr. ? to hear.]
   Pertaining to the sense of hearing, the organs of hearing, or
   the science of sounds; auditory.

   {Acoustic duct}, the auditory duct, or external passage of
      the ear.

   {Acoustic telegraph}, a telegraph making audible signals; a
      telephone.

   {Acoustic vessels}, brazen tubes or vessels, shaped like a
      bell, used in ancient theaters to propel the voices of the
      actors, so as to render them audible to a great distance.