演讲者说完那句话后，人群中立刻响起了一片嘘声。

The crowd erupted in loud ___hissing after the speaker made that remark.

当猫靠近时，那条蛇开始发出嘶嘶声。

The snake started ___hissing when the cat got too close.

高压锅开始发出嘶嘶声时，说明蒸汽正在释放。

The pressure cooker started ___hissing when steam began to escape.