Download music from laptop to mobile

Hi i have downloaded some cd's to my laptop which play perfectly well through the laptop.
I have then downloaded that music to a usb stick and also my mobile.
When i try to play the music from either there is no sound whatsoever yet the titles
of the tracks and albums appear on both. Everything i would expect to be there is
there but i cannot for the life of me understand why there is no sound. So frustrating!
I have been in to an EE phone shop and also carphone warehouse but no one could
help.
I would be delighted if you could help. Many thanks. Chris