2006 Ford Fusion Battery Dying

Electrical problem
2006 Ford Fusion 4 cyl Automatic 46000 miles

I have a 2006 Ford Fusion S and I have now purchased two batteries since this problem started. After the first one died (after one week of buying the new battery), I brought my car to a mechanic and payed for a better, more expensive European battery. Anyway, a week later (again), my battery died and could not start the car without being jumped. I can jump my car just fine and will drive for a few days after, but I brought my car back to the mechanic and he tested everything and he found out that "something" is using up 12V of electricity from my battery when the car is off but they could not specify where it was coming from. I have been messing around with it today and discovered that a noise is coming from my driver-side speaker once I turn off my car and open and close the door, as if I were exiting the vehicle. The noise only starts when this happens. So immediately I assumed it is from the radio. So I disconnected my radio (all cables) and now I don't hear the noise. Is this the problem you think? What shouid I do about this? Is it safe to drive around with these cables being loose from the radio? Because now my "check engine" light and my air bag light is on. Thank you in advance for your advice.

Scott