Acoustically

pertaining to the sense or organs of hearing, to sound, or to the science of sound.
(of a building material) designed for controlling sound.
music.

of, relating to, or being a musical instrument whose sound is not electrically enhanced or modified.
arranged for or made up of such instruments:
an acoustic solo; an acoustic group.

obsolete. a remedy for deafness or imperfect hearing.
contemporary examples

“when jake first played it for me acoustically, i thought he was making a mistake on the timing of the verse,” rubin tells me.
jake bugg isn’t the new bob dylan. he’s the male adele. andrew romano november 18, 2013

adjective
of or related to sound, the sense of hearing, or acoustics
designed to respond to, absorb, or control sound: an acoustic tile
(of a musical instrument or recording) without electronic amplification: an acoustic b-ss, an acoustic guitar
adj.

c.1600, from french acoustique, from greek akoustikos “pertaining to hearing,” from akoustos “heard, audible,” verbal adjective from akouein “to hear,” probably from copulative prefix a- + koein “to mark, perceive, hear,” from pie -kous- “to hear,” perhaps from root -(s)keu- “to notice, observe” (see caveat). acoustic guitar (as opposed to electric) attested by 1958. related: acoustical; acoustically.

acoustic a·cous·tic (ə-kōō’stĭk) or a·cous·ti·cal (-stĭ-kəl)
adj.
of or relating to sound, the sense of hearing, or the perception of sound.