Which Littmann did you buy? And I don't mean to sound smart, but a few other factors:
* if the scope has a turnable diaphragm/bell, are you sure it was turned the right way? I've made that mistake before...I couldn't hear a darn thing and I realized the diaphragm was turned on to the bell side
* are the ear pieces facing the right way?
* are you trying to listen over bone as opposed to the intercostal spaces? Sounds are heard better when placing the stethoscope on the intercostal spaces as opposed to placing it over a rib.
With that said, I have owned 2 Littmann scopes...the Classic II SE during nursing school and then I upgraded to the Cardiology III. Both are great, but I LOVE my cardio one. I have friends who swear by Ultrascopes as well, which run to be around $100 I think. I wouldn't buy anything else other than a Littmann, though.