I am trying to learn pinyin and find it extremely difficult because several times the sound I think I hear in audio courses does not seem to correspond to the pinying in the various pinyin learning apps or courses.
This happens even for elementary words like Zài jiàn, when I hear jiàn  within Zàijiàn in courses the sounds to me seems the sound of jin.
Is it me unable to correctly understand sounds or is there some difference between spoken language and pinyin? 
Does some other learner have this problem?