Audio Systems: basic car stereo, ground connections, turn signals

Question
  How do I stop the buzzing sound when my truck is running? It's lauder when the lights are on. Could it be the ground  

Answer
These are difficult kinds of symptoms to troubleshoot because they are usually not the fault of the unit itself, but the external environment, such as, the car electrical system, ground connections (as you suspected), ignition noises and so on.

Here are my questions for you to help with the analysis:  
1. Does the buzzing sound increase in level with the volume control?
2. Does the frequency of the buzzing increase with engine speed?
3. Does buzzing sound change its sound quality with engine speed?  If so, in what way?
4. When lights are on it gets louder.  Does it get louder when the turn signals are flashing?  When the brake pedal is pushed?

I need to know the specific answer to each question above.  Please keep all the question in your text when you reply so I know all the background.  Thanks,

C