anechoic

/AE0 N IH0 K OW1 IH0 K/
adjective
  1. 1

    (acoustics) lacking echoes; that absorbs sound

    โ€œThe bassoonist settled into the anechoic chamber and prepared for another grueling recording session.โ€

Antonyms

Source: https://en.wiktionary.org/wiki/anechoic