What's the difference between '들었다' and '들렸다'?

ilyana from Learn Korean asked this question.
Let's see the difference ! Go Go Ssing~ ♬

들었어?
Did you hear that? 그거 들었어?
I heard some noise. -> 나는 소음을 들었다.

If you want to use '들렸다' you gotta change the subject.  You can't just use 'a person' as a subject when using '들렸다/ 들리다/ 들려' , but a person's voice is okay.
     Let's see :D

소음'이 들렸다.' Some noise is heard.
나는 그녀의 목소리'를 들었다.' (I  heard her voice)
**Remember!!**
~이/가 goes with 들렸다.   ~이 들렸다/~가 들렸다.
~을 goes with 들었다.        ~을 들었다.  We always need 'an objective' before 들었다.

들렸어?

As I showed you above, there is not much difference in meaning.
but,it seems more like you didn't want to hear it but you couldn't resist it.

ex) 내가 공부하고 있었는데, 어딘가에서 노랫소리가 들렸어.
I was studying, but I heard singing sound from somewhere.

노래 소리가 좋아서 계속 들었어.
It sounded beautiful, so I kept listening to it.

Can you see the difference? ^^ If you have any question, ask me~ :D