inaudible
adj. 听不见的；不可闻的
例句
His voice was almost inaudible.
他的声音几乎听不到。
《柯林斯英汉双解大词典》
His weak voice was almost inaudible.
他声音微弱得几乎听不到。
The whistle was inaudible to the human ear.
这种啸声人耳听不到。
《牛津词典》
