A sound hole was also cut into the back to allow the sound to escape.

箱子的背面有一个音孔，让声音可以释放出去。

As a kind of visual paradox the sound hole was actually a solid protrusion-a cylinder that thrust its circular opening toward you.

作为一种视觉悖论，音孔实际上是一个实心突起——一个将其圆形开口推向你的圆柱体。