How To Reduce Tire Noise/Road Noise (continued...Step 5)

Step 5

Doors.
Road noise penetrates the door's thin metal skin and reverberate within the door cavity. This booming noise exit the door cavity via those big holes in the door's metal panel, penetrate through the plastic door card into the car's interior,

Remove plastic door panel, and look at the big holes in your metal door panel (inner panel).  Look through the holes at the OUTER metal panel. That's the panel where most "enthusiasts" will cover every sq ft with vibration damping sheets. From my experimentation and experience on more than 500 vehicles, that's a waste of money and adding unnecessary weight to the door unless you're a serious car audio enthusiast.
Use small strips/pieces of vibration-damping sheets to do "spot damping" on that panel. Since it won't block or absorb any noise...so go easy with it. If you see a side-impact protection bar, look at the tiny gap between bar and the metal panel. Slide some thin closed-cell foam into that gap. Or use a small piece of damping material. The idea is to add a separation layer between bar and panel. This will tremendously improve the sound of your door closing (which somehow appeals to many car owners).

Then, look at the INNER panel with all those holes (depending type and make of vehicle). Any hole of any size must be covered up. Simplest would be using Dynamat or equivalent. Best would be any "noise barrier" material such as Mass-Loaded-Vinyl which might or might be common in your country. If your vehicle is not a high-end audio vehicle, it's not necessary to cover every inch of that metal panel. It's sufficient to merely cover up those holes.

After performing the above, any residual noise will penetrate the plastic/vinyl door panel. At the underside of the plastic door panel, you can add a thin layer of material to either absorb or block noise. It can't be too thick, or plastic door panel might not re-fasten easily onto the metal door panel.
Experiment and use the thickest possible material.

If you're on a very low-budget, you can use any kind of felt or carpet underlayment or jute.
This can be found under the carpet of most cars. Alternatively, you can use closed-cell nitrile rubber such as Ensolite (USA), or Insulflex or Superlon. If your budget is ample, my favourite method is:
a. Few small pieces of vibration-damping material evenly spaced out.
b. Any "sound barrier" material such as MLV (Mass Loaded Vinyl).
Accumat has a product that features MLV (AMT250) and this MLV is sandwiched between foam. Dynamat's equivalent is Dynapad. But pls note...these kinds of multi-layered sound barriers are usually expensive but highly effective.
c. Follow up with a layer of 3M Thinsulate to absorb and dissipate any residual noise.


Step 6
Front Kickpanel Areas - (eg: behind your throttle pedal)
This is the area where the most tire noise penetrates greatly into vehicle interior as it's extremely close to the tires. For max results, 1 layer damping + 1 layer barrier (eg: Accumat 250, Dynapad etc) + 3M Thinsulate.

In totality, if Step 1-6 are performed, I'm highly certain you'll experience a hugely noticeable significant reduction in road noise/tire noise levels. However, if you still want to go further, the most practical further step is to change to quieter brand new tires.