I can't hear any blood pressures! I've heard them once, but I haven't heard them again since then! I've practiced using the blood pressure cuffs and I know how to use one. My stethoscope is Littmann cardiology III and it's brand new. I know that it is a great stethoscope. However, I do realize that not all stethoscopes work the same for everyone. So, I tried a different one. It wasn't a littmann, just one of the ones my class provided for us. I still couldn't hear anything, and I am really concerned. I have to take a test over blood pressures soon, but I don't know what to do. Does anyone have any advice?