Hey Wheatworth welcome to the forum.
Hotchef & AndyC have both given you some good information on telling when your food is done. So I will try to answer your question about the grill itself.
The change in the sound of the gas may be nothing other than your tank being a little low. As the tank is under pressure I notice when my tank gets a low the sound is not so loud. I am not an engineer so if this concerns you then you should have a professional look at it for you. As to the flame color it should be blue. A blue flame indicates complete combustion. If the flame begins to turn mostly yellow then your grill is not burning properly and you should have it looked at.
Here is a link to some good information on maintianing a gas grill:
Just scroll to the section on gas grills.
Hope this helps.