Seems that even if you lower the exhaust noise that the meshing of the internals in a Briggs & Stratton engine is still loud. The Honda engines are some of the least noisy I have experienced.
Most Briggs & Stratton engines can be fitted with a Lo-Tone or Super Lo-Tone Muffler to help decrease exhaust noise. See link below for catalog numbers and types of mufflers. Hope this helps.