Isn’t it also the case that a big heavy car with gigantic tires is louder than a lighter car with narrower tires? A Tesla Model X is pretty dang loud at 45 MPH, compared to something like a BMW i3 that weighs half as much and looks like it wears bicycle tires.
Absolutely. Basically the volume of sound emitted increases in proportion to the tyre size and speed, and also is affected by its tread pattern.
In short, the road noise from tyres is due to air being compressed by the tread and then released again. It's basically a constant rolling version of clapping your hands.
Modern formulations of tarmac are designed to settle with air channels (called voidage) to provide an exhaust for that air, significantly reducing the volume. If you want more information on a couple of types, look up stone-matrix asphalt or open-graded friction course. Concrete on the other hand is notoriously poor for sound reduction, because the surface is so much smoother.
As a rough rule of thumb, quietened surfaces come in at 6-9db lower than a comparable non-quietened surface.
ARFC is another kind, made of recycled rubber mixed as a secondary aggregate. It's commonly used as a quiet and long lasting surface in parts of the US, and has the advantage of being a good product for using up waste tyres. In the UK we have different compounds, which do similar things. The M4 between Swindon and Bristol is a particular treat to drive on acoustically.
Undersurface is potentially an issue too. For example, concrete surfaced in mono-aggregate based tarmac has a tendency to resonate and "sing". Concrete with undulations does the same, though for different reasons.
Not ATM. I've been thinking of writing a book on acoustics and perception of sound though for about 5 years, which is related to how I know about this sort of stuff. I've also built speakers in my spare time.
I've always been fascinated by sound and how people perceive it. I'm also a classical pianist and guitarist, amongst other things, which may explain it, or be caused by it. Who knows?
It's not something I thought other people would care to read about though, hence never doing it. Maybe time to re-evaluate that.
Small naturally aspirated gasoline engines are also quieter than turbodiesels. With some good noise dampening in the engine compartment and exhaust system some cars are surprisingly quiet even at low speeds. Also, some roads are louder than others (cobblestone being very loud regardless of speed).
I have a weird obsession with road noise and how it relates to road surface construction.