How do you actually find out that the actress' voice is dubbed or not?

I've seen many actresses dialogues getting dubbed in Telugu films as most of them are not much familiar with the language as Telugu isn't their mother tongue.

I have a really stupid question - how do you actually find out whether the actress has spoken the dialogues in Telugu i.e. the voice is not dubbed by any other voice artists but the actress herself? Hearing the actress' actual voice in some interview and then correlating it can be a bit painful, so is there any other way? I know this is a stupid question but I'm a really curious person and I want to know how this is done.

My question is especially aimed to those who have worked in dubbing department of this industry or those who have worked with the actresses.