Noise from the engine at highway speeds is quite high in the cabin of IC vehicles.
Again, I don't know what you are driving or what Vintage but even cars going back 10 years I have driven have not been able to hear the engine at highway speeds. Only way you can tell the engine is running is the things are moving forward and the tacho sitting at 2500 RPM tells you so.
I can't even hear the engine in my 15 Yo ute at 110 nor can I feel it's running due to the vibrations from the road at that speed.
Also, wind turbulence below the hood adds additional noise on the other side of the firewall.
That may be true but I can't hear what is 6 ft in front of me in any relatively modern car through the sound deadening. Where my father lives, if the wind is blowing right you can hear the cars on the distant highway. You never hear engines or wind noise, it's always the sound of the tyres on the road. If it's raining, you can always hear the sound of the tyres on the wet road much louder.
No grille for cooling air on most EVs.
Have you seen how small the grilles are on modern cars and how the main ducting is down low close to the road?
When they build cars, any cars, they put them in wind tunnels and test for this kind of thing. You don't really believe they are going to let cars into production with howling grilles do you?
Ev's in fact have a look of cooling going on for batteries and other things. They may not have a grille at the front but they defiantly have Heat exchangers and fans for cooling.
It's like IC's are made out that these things are not a consideration and they are all made rough as guts where suddenly when the manufacturers build an EV, they suddenly became concerned about NVH. They put what they had learned about NVH into electrics, they didn't just discover it and how to suppress it over night!
Manufacturers of electric cars know that tire noise is the loudest contributor to NVH in their vehicles. Therefore tires are carefully selected and certain compromises are made in performance, durability and price to meet noise targets that OEMs are setting for EVs. For example, the Tesla's were shipping with Goodyear Eagle Touring, 245/45R19, all-season Grand Touring category, with sound reduction foam.
So one could extrapolate from this that if the same Tyres were used, an IC would get quieter or an EV would get louder because it's more to do with the tyres than the Vehicle? THIS sounds logical.
Tyres make such a huge difference to a vehicle. I have 2 sets for my ute, a set of low profile, wide as can fit low profile's with soft rubber and a set of conventional width/ Height for load carrying and towing. The difference in the way the car handles and performs with nothing else changed bar the tyres is astonishing. I have noticed the skinny( er) tyers are more noisy which was unexpected over the low profiles but it is what it is.
The wide tyres are also much better in the wet which is not the way it is supposed to be but again is the reality.
Be understandable if the regular tyres were Cheap rubbish but they were the most expensive and best rated for that size.
I remember the Tyres my wifes new ford came with many years ago, Goodyears. In my younger days I had put retreads on cars and they were better than these things! Drove the car a few times in the wet and the goodyears were shocking and not so flash in the dry either. After she spun it a couple of times carefully going round roundabout fully aware of how bad the things were, we took it to a tyre shop and had them replaced with under 10K km on the car. I said to the guy, bet you don't get many people changing tyres this new. He said normally not unless people want mags and Bigger tyres but when it comes to these things, we get them all the time! I was surprised and asked why, he looked at me and said the same reason you want to get rid of them, they are complete shit that should never be put on any car! He told me he had bought his wife a new car which had these thing on it and she complained and refused to drive it after a month when she figured out it wasn't the car but the tyres it was sitting on.
I heard many accounts of these same tires later on that were fitted to many new cars and all the stories were the same of how they scared the shit out of people in the wet and dry. Put Yokohama's on to replace these round bits of garbage and it was a different car and could be driven the same in the wet or dry with no concerns at all. I don't say all Goodyears are bad but these things were just dangerous.
I have never heard of foam Filled Tyres. Is this a type of tyre or something that can be pumped into any tyre?
Perhaps what the EV crowd are seeing is not the cars are more smooth and quiet then the IC's at all, They just got a set of better tyres with THE ev than what they had put on the IC?
Can't say I noticed ANY difference in the electric I drove with noise and Vibration either in the city or the country highways I drove it on but I'd guarantee it had the tyres replaced and highly likely if they came with anything special from the factory, they weren't even available to be replaced with the same.... Or would have been paid for by the owner either.
Brings up another aspect of EV ownership though... How much are these special tires over decent conventional rubber?