adj. 25B6; adjective UNHEARD, out of earshot; indistinct, faint, muted, soft, low, muffled, whispered, muttered, murmured, mumbled.
INAUDIBLE
Meaning of INAUDIBLE in English
Concise Oxford thesaurus English vocabulary. Краткий оксфордский словарь английского языка тезаурус. 2012