Hello and thank you for your responses. I finally had time to have my wife rev the engine when I was underneath and I have found that the noise sound like it is coming from part of the muffler system, underneath the engine. After looking on the internet it looks like it is the catalytic convertor. It looks like a bunch of wire that is woven together like a basket. There is also signs that it has rusted out.
So, with that info how hard is it to change myself? It didn’t look like it would be all that difficult. It looks like a couple of bolts on either side.