Inaudible (adjective)

Too quiet to be heard.

Origin:

From latin in- (not) + audire (to hear).

Examples:

1. The sound of the mouse in the wall was inaudible.
2. The whisper was inaudible in the noisy room.
3. The inaudible conversation was going on between two people.
4. His voice was inaudible even though he was shouting.
5. The sound of the wind in the trees was inaudible.