Otacoustic

Ot`a*cous"tic (?), a. [Oto- + acoustic: cf. F. otacoustique.] Assisting the sense of hearing; as, an otacoustic instrument.

{ Ot`a*cous"tic (?), Ot`a*cous"ti*con (?), } n. An instrument to facilitate hearing, as an ear trumpet.