How can I remove noise from USRP Bi-Directional Communication design ?

Hello,

I'm recently working on USRP as a part of my Undergrad Senior Project. I'm following the examples of USRP models given with USRP toolbox. I could make the FM Transmission & Receiver working nice. However, later, I was trying to make a bi-directional communication system with FM Transmitter & Receiver. And Here I'm getting a huge problem.

The bidirection system is consisting of a Transmitter & a receiver together in each pc & running at the same time. So Both System A & B has a Transmitter and a receiver. But when I try run the simulation, the audio signal I receive is noisy.

As long I run just a Transmitter in a PC & Receiver in another PC, it works fine, the audio transmits without any problem, but as soon I run both Transmitter & Receiver in both PC, noise is almost ruining the purpose.

Now, I've been searching for a solution for quite long but couldn't find anything similar. Can you please help me out here ?

P.S. I'm running MATLAB 2013a 32bit