老师的响亮声音在教室后排都能听到。

The teacher's loud ___voice could be heard at the back of the classroom.

他担忧的声音透露出他对她安全的关心。

His worried ___voice revealed his concern for her safety.

当她讨论机密事宜时，她压低了声音。

She lowered her ___voice when discussing the confidential matter.