A "loud sigh" means she thinks you are an idiot at that moment, and wonders why she is wasting her time standing here arguing with you over "Nothing".

一声“大声叹息”意味着她认为那一刻的你是一个白痴，而且不明白自己为什么浪费了这么多时间站在这里来跟你争论“无关紧要的事”。

youdao

Here the chaste Sarah heaved a loud sigh.

这时，贞淑的萨拉高声叹了一口气。

youdao

He snarls, then huffs out a loud sigh and stomps from the room.

发出一个大声的叹息，跺脚走出他的房间。

youdao

Then, after they acknowledged they had a verdict and filed out, Simpson let out a sigh that was loud enought to almost echo in the courtroom, as if he were deflating.

CNN: Returned verdict catches everyone off guard