What is the difference between 듣다 and 들리다?
I know that 듣다 is to hear and 들리다 is to be heard. I guess I'm just wondering how do you know when to use which one?

Question

What is the difference between 듣다  and 들리다?
I know that 듣다 is to hear and 들리다 is to be heard.  I guess I'm just wondering how do you know when to use which one?

Answer

'듣다' means 'hear something'.
I hear a strange sound. (이상한 소리를 듣다.)
'들리다' is a passive form of '듣다'.
A strange sound is heard. (이상한 소리가 들리다.)

Answer

나는(s) 노래를(o) 듣는다.(v) 
노래가(s)  들린다 (v)

There is no object in passive sentence.

Answer

Thank you!!!  This makes a lot more sense now.  At first I thought they were two individual verbs and not one being the passive of the other.  Got it.  Thanks!