The double-wall factory stock pipe & silencer of a KDX are very quiet.
Performance modification means replacing the stock system with an aftermarket expansion chamber and silencer, and opening-up the air box for freer intake air-flow.
The price is increased noise.
The dB Snorkel will help get some of that stealth back, but it will probably never be as quiet as the KDX factory stock system.
Noise is additive:
Because of (single-wall) expansion chamber and air box noise, the rider might not notice a dramatic noise reduction from the dB Snorkel. We have yet to hear of a KDX rider who gave up wearing ear plugs because he had a dB Snorkel.
The noise exiting the end of the aluminum silencer carries farther than the “ting” from the expansion chamber or the rattle from the air box.
It is the exhaust noise that your neighbor hears.
By using the dB Snorkel you will, in effect, increase your “noise buffer zone.” - And you will be doing it while maintaining exhaust flow.