Insulation can be installed in a unit. There are, however, a few things to keep in mind when searching for a dampening material.
Soundproofing Home Appliances
GDP645SYNFS by GE Appliances - GE® ENERGY STAR® Fingerprint Resistant Top Control with Stainless Steel Interior Dishwasher with Sanitize Cycle & Dry Boost
How to Replace a Dishwasher (in 6 Easy Steps) - Dan Marc Appliance
GE 24 in. Fingerprint Resistant Stainless Front Control Built-In Tall Tub Dishwasher with Dry Boost, 3rd Rack, and 47dBA GDF650SYVFS - The Home Depot
How to replace Sound Insulation part # W11086533 on your Whirlpool Dishwasher
How to Remove a Dishwasher (10 EASY STEPS)
How to Install Insulation for Your Dishwasher
GE WD30X28658 Dishwasher Tub Insulation Blanket WD01X10206 WD01X10259 WD01X10260 WD01X10266. Part Number WD30X28658 replaces WD01X10089 WD01X10206
OEM GE WD30X28658 Dishwasher Tub Insulation Blanket WD01X10206 WD01X10259 WD0
Water Heater Energy Saving Tips