Dropping 11db will definitely be quieter.

IIRC an increase of 10db is the equivalent of doubling the perceived volume.

Good on ya for being concerned about noise. This issue alone is one of the main reasons the anti-atv crowd keeps trying to close more of the dunes and trails in my neck of the woods.

 

sounds like i have the same setup as you. i have a 07 400ex with hmf sport series slip on. the quiiet core and it is definetly helps a lot. it may not seem like it at first but ride with it and then without it and you will see what i mean. IMO def worth the $20

 

I put the HMF Sport series with the quiet core on my wife's 400ex and it meets the Oregon dunes 94db level.

 

Good deal, then I hope mine will be noticably quiet. I took my end cap off today and did not find a baffle or a spark arrestor. Just looked like it had packing in it but I could see straight down the middle to pure darkness. Now is this normal or did the previous owner remove stuff? Ive never looked inside one till today.

 

That is normal.

 

My quiet core came in today. So I took a good ride before and after the install. I must say it is way quieter. It has the sound of my warrior which is stock. Now dont get me wrong, when I peg the throttle it is still loud but I would say it knocked half the sound out. it also changed the tune so it is not that real deep sound that carries. It was well worth the money for this thing.