anechoic (adj.)

privative prefix, from Greek an-, "not, without" (from PIE root *ne- "not"). The Greek prefix is a fuller form of the one represented in English by a- (3).

1880; see echo (n.) + -ic. A word from the OED.

Onomatopoeia, in addition to its awkwardness, has neither associative nor etymological application to words imitating sounds. It means word-making or word-coining and is strictly as applicable to Comte's altruisme as to cuckoo. Echoism suggests the echoing of a sound heard, and has the useful derivatives echoist, echoize, and echoic instead of onomatopoetic, which is not only unmanageable, but when applied to words like cuckoo, crack, erroneous; it is the voice of the cuckoo, the sharp sound of breaking, which are onomatopoetic or word-creating, not the echoic words which they create. [James A.H. Murray, Philological Society president's annual address, 1880]