High-pitched sound when my lights are on

I was an idiot and left my lights on when I parked my car at the airport for four days. Of course my battery was dead and my battery was jumped (note the person who gave the car a jump reversed the polarity, quickly noticed and reversed his connections).

Now, when I turn on my headlights there is a nearly unbearable high pitch noise coming from what I think is the stereo system. The clock no longer works. The sound continues to blare if I then turn off my light, but I notice there is a change in the pitch when toggling the lights on and off. There does not seem to be a correlation between the sounds and whether the engine is running or not.

What can I do to fix this?

The car is an 1989 Toyota Corolla DX

I would only speculate as to the exact electronic component that has been damaged but I do believe your car/electrical system has suffered damage from the reverse polarity incident.