It is impossible to make your hub louder without damaging it or making it more likely to wear. Your hubs noise depends on things like how many pawls are used, how tight the spring is, how dry the inside of the hub is and how deep the engagement points are. If you have to make it louder tightning the spring around the pawls or cleaning out the lube will make the hub louder but will also make it wear quicker. NEVER cut(deepen) the engagement points though . Some dirt jumper came into the bike shop i work in a while back who had done this and it was unfixable. Not worth the risk. Best bet would be to just leave it as is if your happy with it though.