The horn that sounds when you lock your doors and my normal horn sound deflated. Is this because of a week battery or what?

 

You may have crap built up in it.

 

Could be something in the horn, or it could be dirty contacts in the horn relay ( 2008 this is non serviceable ).

You can check the horn connector, to make sure you have the correct voltage, with someone pressing on the horn. That would rule out a problem with the circuit.