She can hear me on Skype but I can't hear her?

Quick question, I was talkin with my friend on Skype the other day, we were talking fine, then when she put in her headphones, with a built-in microphone, I could not hear her, she however, could hear me clearly but I could not. I was just wondering what could be the issue, again, it is the microphone built in to her headset. I hear this fuzzy noise similar to that of a heart beat (same rhythmical pattern).
So I'm just curious, she has had an iPhone 4S, I'm using an iPod 4G, what could be the issue? She checked her settings and all looks good!

Consult an ENT doctor! J4F.

The problem could be with the headset that your friend used. Like some headsets doesn't coincide with the wavelength of the devices and give this prob! Change the headset!