airbox mod, now engine is louder...why?

[ChrisRl]

Well I removed the airbox from my KLR 250 and drilled some extra holes near the intake periscope. The air intake area is now about x3. I cleaned the box and replaced it. Now when the engine is seriously pulling, revs high or low the engine is noticably louder, more of a hollow and loud sounding engine noise. Why is this? Something to do with the petrol/air ratio? Would it be lower with air finding its way into the carb easier now? I know I'm a bit alone on this as this mod is on a 250...but in principle you 650 guys should have a few answers. Would altering the carb for a slightly richer mixture reset matters and provide some more power....perhaps? Cheers, Chris.