soundlessly
/ˈsaʊndləsli/ 8"Soundlessly" means without making a sound or silently. For example, "He slipped soundlessly into the house".
adverb [方式副词]无声地；静悄悄地；完全静寂地
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。
单词造句:
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。