If you want to reduce the noise, put Mass Loaded Vinyl under your floor mats. We put Dynamite on our floors and doors with little noise reduction but the MLV does the trick. We have an EX-L. If you decide to do the door panels you only need to cover about half for full effect; we covered it all prior to reading that cost saving recommendation.
This is correct.
Do NOT waste hundreds buying too much dynamat, that is not the intent of the product, it will not work, and it can cause problems with maintenance and repairs to put large sheets of the stuff where it doesn't belong, and potentially trap water and lead to rust.
Dynamat and other butyl dampeners are for reducing vibration and resonance noise in the metal parts of your car. It is a small part of noise reduction and the factory already applies this to many areas. If you are going to instll a butyl dampener like dynamat, you only need about
25% coverage of any metal surface, using small pieces, and only on surfaces that are not rigid like outer and inner door panels, large floor or roof panels that don't already have factory dampener, etc. Using much more than
25% coverage makes almost zero difference, but is popular because the manufacturers do nothing to dispel the myth and customer think more is better. Independent testing verfies how little you need. I suggest secondskinaudio over dynamat; It is similarly priced but goes further and is a better product due to its foil thickness and weight. They also sell MLV and foams appropriate for car evironment. Their MLV is over priced and you can find the same for cheaper elsewhere.
As mentioned by Devers, mass loaded vinyl MLV will reduce many frequencies well as it is heavy and absorbs sound energy. It must be decoupled from metal panels by at least 1/8th inch of something soft like a closed cell foam so it is not bonded to the metal and won't resonate. Carpet works, and this is why doing most of the floor under the floor mats through out the car can reduce noise. I hung a sheet of MLV in each door panel and got the most noise reduction from all the treatment in my project. Adding more to the floors helped significantly also, especially draped over the entire cargo area and under the rear seat and front mats. Make sure you buy virgin MLV to avoid getting recycled material that will smell and release VOCs into your cabin.
In pillars, door cavities, and roof you can use melamine foam to absorb high frequencies that bounce around those spaces or enter from them. All foam installed MUST be the type that will not hold water (closed cell foam for decoupling MLV and hydrophobic open cell melamine foam for cavities and large metal panels to absorb high frequencies).
Unplugging the ANC active noise cancellation under the dash also unplugs the idiotic fake exhaust sounds your car plays in the cabin. Yes, really. So emberrassing for Honda and the other major brands who do this. The ANC module does very little if anything at all to reduce road noise, and once the sound is gone you realize how annoying it was.
I have been much happier since treating my Passport for noise. Some may say too much labor, I say it was one weekend for years of greater peace for each mile driven. With quiet 18" tires it rivals some luxury cars. Total cost of the sound deadening project was about $600-700 and a couple long days in the garage.
I would advise if this is something you want, do some research in to the proper materials and installation first. Just slapping in products is a way to use a lot of money for little to no effect and may even cause issues you have not considered.
I would post pictures of the project if I can find the audio thread I put them in....
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