‘listen (to)’ or ‘hear’?

We use hear to say that something that comes to our ears.
Example:

I can hear a strange noise upstairs.

BUT

We use listen (to) when we talk about paying attention to sounds that are going on, in progress. It stresses on the idea of concentrating, trying to hear as well as possible.

Example:

Listen carefully. That’s a tiger growling!

You can hear something without wanting to, but you can listen to something only deliberately.
Compare:

I heard them talking upstairs but I didn’t really listen to their conversation.

However, listen (to) is mostly used to talk about concentrating on experiences that are going on or in progress. To talk about the result of listening (experiencing the whole of a performance, speech, piece of music or any broadcast) we generally use hear.

Example: I heard the Prime Minister’s speech to the nation on radio yesterday. It was indeed very inspiring!

Also, hear is not used in continuous form.

Compare:

I can hear somebody coming. [correct]
I am hearing somebody coming. [incorrect]