声波遇到障碍物时,将在界发生反射。遇到障碍物被反射回的声音叫做回声。人站在山谷中大声喊话时,以听见几次回声。这是声音在传过程中遇到障碍物时会发生反射缘故。由于声音遇到了远近不同障碍物被反射,且反射回来的时间先后不同,所以往往可听到几次回声。回声的形成具有一定 When the sound wave encounters an obstacle, it will reflect in the boundary. The sound reflected by obstacles is called echo. When people stood in the valley shouting loudly, they heard several echoes. This is the reflection of the sound when it encounters obstacles in the process of transmission. Because the sound encounters distant and near obstacles and is reflected and reflected back in different times, it is often heard several times. The formation of echoes is certain