Parrot 3200 poping sound

I have the 3200 LS installed in a 2005 chevrolet truck.  Everything works great, except while driving if I hit a few bumps in the road I can hear a poping sound from the front left speaker, but it doesn't do it all of the time.  If I am talking on the phone and this happens, the person on the other end can hear me, but I cant hear them, if I am lucky enough to hit the right bump the speaker comes back on and everything is fine.  Another note, while playing the radio,  the sound never goes off, just when I am talking on the phone.

I have checked my connections and all seem to be ok.  It is almost as if there is a short somewhere, but the unit never actually shuts down, just the speaker.

Any idea what may be causing this?

Thanks