说明： 在某个音乐厅内，原始音频信号的回音由于墙壁和天花板等的反射而产生，听众所感受到的音频信号是 和它的回音的合成 (In a concert hall, the original audio signal echoes, such as walls and ceilings as a result of the reflection arising from, the audience may not feel the same audio signal and its echo is the synthesis)
