Elon has mentioned that his cars could be made quieter with 500 lbs of dampener and insulation. That is what the luxury auto makers do to hush their cars. Also switching to framed door windows would reduce sound levels.
Downside is that it adds weight, reduces range, reduces performance, costs more, and generally reduces efficiency.
Hush is a big selling point with the higher priced Mercedes, Lexus, BMW, and Rolls Royce.
Other manufacturers go the other way, by fitting loud exhausts, loud engine intakes, phony sound system noises and ported sounds piped from the engine compartment. All go towards the total overall experience they desire. Some even lower the drive ratios so their cars can spin the tires, burn rubber and lay patches. Makes the driver feel the car is more powerful.
Tesla has been generally making their cars quieter over the years. It is not quite the level of the luxury brands, but they have added some insulation, double paned side glass, better gaskets etc. Their automatic noise reduction system is tuned to reduce low frequency sounds when driving over rough roads.