I tried some sticky back shiny front stuff, I think from Lowe's [or maybe Home Depot] some years back. 
It quieted things down nicely but when the weather got hot it slowly slide down the inside of the doors, gumming up the window winding mechanism.
So be careful when choosing shiny side sticky black back stuff!
JME
Mikefrom Cotati 

     On Thursday, August 6, 2015 9:27 AM, Richard Koerner <rjkinpb@SBCGLOBAL.NET> wrote:
   

 Lowe's has it, not Home Depot.
    From: Karl Wolz <wolzphoto@Q.COM>
 To: vanagon@GERRY.VANAGON.COM 
 Sent: Thursday, August 6, 2015 9:15 AM
 Subject: source for peel-n-stick sound deadening
  
This subject has been brought up a few times.  I thought someone mentioned a product from Home Depot, but I couldn’t find anything there.  Thoughts?

Thank you,

Karl Wolz