根据以下输入和给定的规则，编辑文本中的句子结构。
- 原文本：The cat slept peacefully on the windowsill, while the dog barked loudly outside.
- 编辑规则：将两个句子合并为一个句子，并改为被动语态。
While the dog barked loudly outside, the cat was peacefully sleeping on the windowsill.