Dear Car Talk:
I was wondering how much traffic noise comes from engines and how much from tires on pavement? My house is near an urban expressway.
Will our neighborhood get any quieter when all vehicles are electric and there are no internal combustion engines on the road? -- Larry
Internal combustion engines make the most noise when they're working hard -- like when they're accelerating or moving a car up a hill. And they're not generally working that hard when a car is just cruising down the highway.
If you're near a flat section of highway, Larry, those cars are in high gear. That means most of their engines are turning at a modest 1,800 to 2,500 rpm. So, the bulk of the noise you're hearing is tire noise.
You can confirm this yourself. Next time you're cruising down the highway, turn off Beyonce for a moment and see what you can hear most -- the engine or the wind and road noise. It'll be the latter.
Sound energy doubles for every 10 mph or so of speed. So road noise from traffic at 70 mph is going to be a lot louder than road noise from 30 mph traffic. As you and your family can attest.
Electric cars are more likely to help with noise on slower and residential streets, where acceleration can make as much noise as tires. And they'll be particularly helpful in reducing noise when large trucks go electric. That'll help your situation, Larry. But electric drivetrains, on their own, won't solve your highway noise problem.
The good news is there are other technologies that may help. Lots of places are using rubberized asphalt to pave roads now. That's asphalt mixed with bits of old tires. Kind of a homeopathic approach. Tire vs. tire. Those roads are a lot quieter. And there are experimental road surfaces being developed that might reduce noise even more.
And in the meantime, there are noise-canceling headphones.