Fake engine noise is a thing. Ford now puts it in their trucks.[1] A DSP synthesizes V8 engine sounds, which are played through the audio system. Here's how to disable it.[2] (This is for engine noise inside the cabin, not for pedestrians. Outside noise generators may be required for very quiet cars, but they will shut down around 35MPH.)
Modern engines just are not that noisy. People need to get over this. They got over sudsy laundry detergents. In the 1960s, it was a selling point for detergents that they generated lots of foam. This was a holdover from the soap era. Laundry detergents don't need foam to work, but people expected them. And customers wanted long-lasting foam, which resulted in sudsing agents which would survive all the way through the sewerage disposal plant and into lakes and rivers. That resulted in EPA regulations which ended the suds wars. Now, nobody wants suds from laundry detergents.
Modern engines just are not that noisy. People need to get over this. They got over sudsy laundry detergents. In the 1960s, it was a selling point for detergents that they generated lots of foam. This was a holdover from the soap era. Laundry detergents don't need foam to work, but people expected them. And customers wanted long-lasting foam, which resulted in sudsing agents which would survive all the way through the sewerage disposal plant and into lakes and rivers. That resulted in EPA regulations which ended the suds wars. Now, nobody wants suds from laundry detergents.
[1] https://www.washingtonpost.com/business/economy/americas-bes...
[2] http://www.f150forum.com/f118/active-noise-control-fake-engi...