A car radio volume control governed by the speedometer. You’d get volume on highways where the road and wind noise are great, but no blaring in town.
B.L.Broadwell, Towson, Md.
I think a lot of cars have this built-in these days. I know my car has a setting on the onboard computer display that allows the volume to be set to automatically increase as your speed increases.
If you’re looking to purchase a car radio you buy one from Amazon such as this Pioneer one, although, it doubt it will adjust your volume as your speed increases! (affiliate link)