subaudible

adjective

sub·​au·​di·​ble ˌsəb-ˈȯ-də-bəl 

variants or sub-audible

1

: too quiet or obscured to be heard clearly : inaudible or barely audible

… swaying in time with the rhythm, whisper-singing along at a subaudible level …

—Karen Ravn

… subaudible messages, i.e. auditory stimuli which are played at a low volume and under … music, ocean waves, etc. so that they cannot be heard.

—Geoffrey P Lantos

2

: infrasonic sense 1

subaudible tones/frequencies

Word History

First Known Use

1837, in the meaning defined at sense 1