Inaudible means too quiet to be heard at all. Almost inaudible, inaudible from the back, an inaudible reply.
It is a threshold word: something is inaudible or it is not, at least for a given listener at a given distance. Transcripts mark unclear passages as inaudible, which is a standard convention in court and broadcast records. Note audible; and that the Latin means not able to be heard, from audire — the same root as audience and obey.
1adjectiveinaudibleToo quiet to be heard at all.
“Her voice was so soft that it was almost inaudible at the back of the hall.”
inaudible is a quality of being unhearable.
In- plus audible, from Latin audire, to hear. Audio, audience, audit and obey come from the same hearing.
Proto-Indo-European
*h₂ew-
Latin
audibilis
Middle French
audible
English
audible
English, today
inaudible
From in- + audible. audible Middle French audible, from Latin audibilis, from Latin audire (“to hear”).
Etymology from Wiktionary, CC BY-SA