I've had some loud tires in my life and I've never noticed a difference depending on air pressure. Some tires (knobbies, especially) are just loud on the road. It's just one of those things.
Earth Cruiser worked closely with GMC to create this concept. It looks pretty cool, I must say. Here's what they have to say about it:
You can learn more about it here: https://earthcruiser.com/reserve-your-gmc-hummer-ev-earthcruiser/
Here are additional images as well: