Early 17th century (in an earlier sense). From ancient Greek ὠτ-, οὖς ear + ἀκουστικός acoustic. Compare ancient Greek ὠτακουστής, French otacoustique, adjective and noun.
Definition of otacoustic in US English:
otacoustic
adjectiveəʊtəˈkuːstɪk
That assists the sense of hearing. Now rare.
Origin
Early 17th century (in an earlier sense). From ancient Greek ὠτ-, οὖς ear + ἀκουστικός acoustic. Compare ancient Greek ὠτακουστής, French otacoustique, adjective and noun.