From Longman Dictionary of Contemporary Englishldoce_002_cacoustica‧cous‧tic /əˈkuːstɪk/ ●○○ adjective 1 
Crelating to sound and the way people hear things2 APMan acoustic guitar or other musical instrument does not have its sound made louder electronically → electric —acoustically /-kli/ adverb
Crelating to sound and the way people hear things2 APMan acoustic guitar or other musical instrument does not have its sound made louder electronically → electric —acoustically /-kli/ adverbExamples from the Corpus
acoustic• Possible swap for interesting electric or acoustic.• It is known that there are few, if any, reliable acoustic cues to word boundaries.• The noises you heard - the explosive noises - were the acoustic effects of a second Darkfall strike.• Various pieces of recording equipment are used to produce interesting acoustic effects.• Deaf people get no acoustic feedback when they talk, so their speech is often impaired.• The insects that bats prey upon have a comparable battery of sophisticated electronic and acoustic gear.• Budd, who has been strumming his acoustic guitar through the Midwest, writes introspective songs with a witty, sincere touch.• Unfortunately, the beginnings of utterances appear to be particularly unconstrained by either the acoustic material or the linguistic interpretation.• It is this industrial market that excites potential manufacturers of acoustic microscopes.• The vibration takes the form of an acoustic wave travelling down the rod.Origin acoustic (1700-1800) Greek akoustikos “of hearing”, from akouein “to hear” 