Sound Deadening
  Even tough Jazz has significiant sound insulation material installed compared to former Honda models, road noise is still a problem. Some road noise is coming thru doors. After adding sound deadening panels and some sound absorbing foam sheet inside the doors,  the result was great, humming noise disappeared. Road noise reduced.Door become heavier and tin-like sound while shutting it has turned a firm "thunk" sound. Speaker's bass become better. Total cost was only 30 USD.
First step is removing door panels. There are three plastic tips under the door handle. Press firmly with a flat screwdriver. Then pull the handle, it will easily come loose. To see detailed description of removing door panels, See
There are 3 screws inside and there's one screw on the door opening handle. Take them out, take off the electic plug for window openers.
When you take out the door panel, there's a nylon fog cover. It's glued to inner door sheet with a sticky material. Sound deadening material will be added to the outer door bare metal pointed with yellow arrows.
Deadening material is a self sticking asphalt based, flexible, heavy sound insulation panel. There are several brands on the market having different characteristics and prices. I've chosen the cheapest. It's called Tander and produced by Dupont. 
 I have applied the tander to any surface over the outer and inner door sheet metal. Normally sovering half of the bare metal will suffice. We don't want to make the door very heavy, it may affect the door joints.
I  put the original nylon cover back.
Sound absorbing foam, which can be found in any hardware store, it's used for home insulation but working great on car doors. I've sticked it over the nylon cover with double sided duck tape.
Rear doors are also processed. The problem is removing the door panels. Otherwise it's an easy process and really worth the effort.