Inflatable tires are the best insulator for both bumps and road buzz. Wider tires are better because you can run lower air pressure to absorb vibrations. Avoid tires with stiff side walls and heavy tread. Those tires are good at preventing flats but transmit a lot of vibration. It is difficult to find high quality wide tires that are flexible but they are the most comfortable.
We ride a lot of chip seal, and washboard roads as well as roads that have pot hole patches patching more patches. We started on narrow high pressure tires and have migrated to wider lower pressure high quality tires.
Another thing to think about is how much weight you have on your hands. Road vibration is more manageable if your bike fit allows you to ride with a light touch on the handlebars and little weight supported by your hands and wrists.