inaudibly

not-comparable

In a manner which is incapable of being heard or not loud enough to be heard.

Japanese Meaning

音が聞こえないほどに / 十分な大きさで音が出ず、聞こえない状態で

She whispered so inaudibly that even her closest friend couldn't make out the words.

彼女は声が聞こえないほど小さくささやいたので、親しい友人でさえ言葉を聞き取ることができなかった。

Sense（1）

In a manner which is incapable of being heard or not loud enough to be heard.

The cat scampered inaudibly across the floor.