Do you have the context where it was used? This doesn't really make sense to me, but it probably would be something like a person getting louder and louder until he was being rude with his volume.

This sentence doesn't make much sense. The context may help come up with a meaning. Bombast means speech too pompous for an occasion or pretentious words.

I agree with the others, this is not proper English. It sounds like a foreigner who is trying to say that someone is becoming louder and talking more nonesense until they are ranting bombastically.