What does acoustic mean?
The definition of acoustic
A*cous”tic (#; 277), a.
Etym: [F. acoustique, Gr.

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.

A*cous”tic, n.
A medicine or agent to assist hearing.