So, I have the plastics off my Z since I just did a battery relocate and was thinking about doing some sound proofing before I put it back together.  Anyone have suggestions of what I could put on the back plastics or any tips to help make this 500 more quiet?  I like to be able to communicate to my passengers.  I still have air intake in the cab but blocked off from the rear the "pizza box" mod.

[2015 Z Force 800 53/Trail EPS]

I had a couple of extra rolls of this stuff left over from another project so I used it on my Z.

https://www.amazon.com/CHAOGANG-Deadener-Deadening-Insulation-Self-Adhesive/dp/B099PT5JK4/ref=sr_1_27?crid=PR36YD88J3RT&keywords=automotive+sound+deadening+material&qid=1643387555&s=automotive&sprefix=Automotive+sound+dead%2Cautomotive%2C106&sr=1-27

You will want to clean up the surfaces before custom-cutting each section and use a roller to get 100% application. All the rear cab plastics, as much of the under-side of the floor, the center tunnel and the engine-side of the rear cargo box. As my intakes were relocated I was also able to seal-off the center grilling with it. Probably only a 3dB reduction but it is noticeable...that and the addition of the BENZ Silent Rider cut at or over 4dB noise in the cab. A lot of work but..any noise reduction is worth it. Now mostly what I hear is the drive train whining. I also used chunks of memory foam to plug-up holes like where the seat belts bolt down and those behind and to the side of the seats. Shot a little black spray paint over the top to hid it some. I also put a boot on the E-brake. Every little bit helps.         

I had a couple of extra rolls of this stuff left over from another project so I used it on my Z.

https://www.amazon.com/CHAOGANG-Deadener-Deadening-Insulation-Self-Adhesive/dp/B099PT5JK4/ref=sr_1_27?crid=PR36YD88J3RT&keywords=automotive+sound+deadening+material&qid=1643387555&s=automotive&sprefix=Automotive+sound+dead%2Cautomotive%2C106&sr=1-27

You will want to clean up the surfaces before custom-cutting each section and use a roller to get 100% application. All the rear cab plastics, as much of the under-side of the floor, the center tunnel and the engine-side of the rear cargo box. As my intakes were relocated I was also able to seal-off the center grilling with it. Probably only a 3dB reduction but it is noticeable...that and the addition of the BENZ Silent Rider cut at or over 4dB noise in the cab. A lot of work but..any noise reduction is worth it. Now mostly what I hear is the drive train whining. I also used chunks of memory foam to plug-up holes like where the seat belts bolt down and those behind and to the side of the seats. Shot a little black spray paint over the top to hid it some. I also put a boot on the E-brake. Every little bit helps.
     

Thanks for the advice.  After thinking things over I think I'm just gonna roll with some noise cancelling earbuds.  In fact, I'm gonna make some comms out of them and some cheap radios.  That way it will eliminate the sound, while at the same time letting me talk to my passenger as well as others I am riding with.