I mounted a stealth muffler on my RZR, it mounts to the out put of the stock muffler. While riding in the RZR it reduced the apparent noise level about 30 %. If you are trying to quiet a motor for hunting, the drivers seat is not the place to judge the noise level. My exhaust points to the ground. Another person drove my RZR, When they got about 50 feet from me, the noise level dropped significantly. I figured out that closer than that, I was hearing the muffler and the echo noise from the ground. After 50 feet all I was hearing was the muffler. My RZR was a lot more quiet then I thought it was. After It had gone behind my house, I could not hear the machine at all. So if you are trying to quiet a motor, have someone else drive it away from you before you modify it. That will give you a bettor reference point for how quiet it is. I am sure they have a meter to measure decibel level, but I have not seen one. I think ears probably work good enough except for determining an accurate per cent of noise reduction.