Acoustic

Part of speech: noun (n.)

A medicine or agent to assist hearing.

Part of speech: adjective (a.)

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.