Originally Posted by F.I. Inc.

Great inquiry about what amount of noise cancellation the resonators do to the exterior sound level. That being said, this thread will be 4 years old as of this summer. This is actually a continuation of the original thread which was over 500 pages long. Now up until this point I really did not get asked about the exterior noise reduction all that often. Sure, I have been asked this question in the past but not enough to really make me think its a vital piece of information being left out. 99% of the time people are more concerned with the interior noise level over the exterior.

Now I can promise you after over 700 exhaust systems sold that nothing about our products are mis leading. I do understand where you are coming from though. In fact, I think you are on to something. I will update the website as well as the first page of this thread to try and give the potential customer as much information as possible.

As you already know, the resonators are strictly noise canceling devices. They do not hinder the performance at all.

Non Resonated
By far the loudest and most unrefined. Very exotic tone with a substantial amount of interior cabin noise. With stock cats I think it will be more than tolerable. With the addition of HFC's or TP's (unless you want it loud) I always recommend the 12" or even the 18". Outside the car: very loud and somewhat F1 inspired. The tone will be higher pitched.

12" Resonated
Right around 30% quieter inside the car and 15% quieter outside the car. As you can see, the resonators will effect the interior noise level much more than the exterior noise level. In addition, the 12" resonators will create a deeper, fuller and smoother tone across the entire RPM band.

18" Resonated
The quietest option out of the three choices. Roughly 50%-55% quieter inside the car over the Non Resonated and 25%-30% quieter outside the car. Again, you see that the resonators will effect the interior noise level much more than the exterior. Just like the 12" these will create that same deep, full and smooth tone throughout. This option is very practical for everyday driving especially if the stock cats have been removed. The 18" resonators will do a superb job in balancing the sound level back out.

I think that this covers it for now. If you have any further questions, please do not hesitate to ask.

Thank you, Tony