The sound of dolphin is inaudible to human ear due to it's high sound frequency.

人类听不到海豚的叫声，因其声音频率很高。

Her voice is so weak that it is almost inaudible.

她的声音微弱得几乎听不见。

The horn of the cars on the road made my voice inaudible.

马路上的汽车鸣笛声完全淹没了我的声音。

His voice was almost inaudible.

他的声音几乎听不到。

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。

Student: inaudible Prof.: good.

学生：,教授：好。

Student: Inaudible Prof: who was it?

学生：，教授：谁？