soundlessly
adv. 无声地；静悄悄地；完全静寂地
例句
Joe's lips moved soundlessly.
乔的嘴唇无声地动着。
《柯林斯英汉双解大词典》
I crept upstairs and tried to open the door soundlessly.
我蹑手蹑脚地上楼，悄无声息地打开门。
As I watched she turned, crept soundlessly from the room and was gone.
就在我注视戴比的时候，它转过身，静悄悄地出了客厅走了。
