how would you know how to pronounce it, if you never heard it:)
and this is the beauty of Polish ... Learn the pronunciation rules and a great deal of what you vocalise will be pretty close*. It's not like English where you need to learn the pronunciation of word after word after ....
Unfortunately it's a bit of a two-edged sword - I can read stuff out loud that is passably-understandable to someone listening, but which I don't understand at all :D
*given the expected difficulties with some sounds - for me they represent a physical problem of delivery unrelated to my head knowledge of the sound.