And for people who use their voices a lot, like singers or professional speakers, get voice training and use an amplifier.

VOA: special.2009.09.02

Because the condition of the amplifier this morning, you can't hear what that is.

因为今天早上功放有点问题,你没法听清到底是什么

耶鲁公开课 - 聆听音乐课程节选