So far I've been noticing that 'Jij' sounds like 'Yay' in English, while 'Je' sounds more like an unstressed 'ye.' (Like saying 'yus' without the s at the end) Play the audio slowly to see the difference easier. Also, correct me if I'm wrong, but I believe that 'Jij' emphasizes 'you' more in the sentence. (Ex. YOU are a girl) 'Je' is just an un-emphasized form of 'Jij.' (So you would use 'Je' in a sentence like 'I walk to the bus with you.') Hope that helps!