Friday, July 17, 2020

Road noise and what we can do about it

I'm really noise sensitive.  Perhaps you are, too.  I did some research reading and am collating it here.

(My local main street of Artesia Boulevard is painfully loud.  My ears ring after I've walked more than a couple of blocks along it.)

First off, I found a recently published book that has an entire chapter about Traffic Noise By Sanja Grubesa and Mia Suhanek. BTW, I just learned about IntechOpen, an open access science book publisher. This is so much better than the for-profit model. I'm looking at you, Elsevier Press.

Brubesa and Suhanek wrote a concise and excellent chapter. I'm excerpting a little bit but I hope you click on the link and read it yourself.
Road traffic noise depends on the following three factors:
  • Type of road vehicles.
  • Friction between the vehicle wheels and the road surface.
  • Driving style and driver behavior.
What types of vehicles?  In general, bigger vehicles produce more noise.

Electric vehicles don't produce any engine noise. Some hybrids run in all electric mode at low speeds (below 10 mph for our family's car.)  In congested city driving, electric and hybrid cars reduce traffic noise relative to normal ICE, Internal Combustion Engine, ones.

Vehicles also produce wind noise from the turbulent air that they produce as they travel.  Blocky vehicles create more turbulence.  Aerodynamic ones produce less.  Many economy cars and older minivans are wedges on wheels, delivering better fuel economy and less noise than trucks and SUVs.

The fashion for making minivans "cooler" by shaping their front ends to be more vertical and blocky like SUVs is so bad for noise, fuel economy and public safety for everyone outside the vehicle.  SMDH

Tire noise is a major noise generator.  Tread matters.  If you ride a bike, listen to the difference between smooth and knobby tires.  Car tires are similar, only the car cabin insulates you from having to hear the noise of your tires.  Everyone outside your car notices and is cursing you.

In general, the larger the tire-street contact area, the bigger the noise.  So you may buy the bigger tires for more cabin comfort/smoothness, but you are creating more friction and making more noise.

The heavier the vehicle, the greater the noise.  So EVs have silent engines, but may have greater tire noise.  To have decent driving range, their batteries are heavier than carrying an engine and a tank of gasoline.

The faster the driving, the greater the wind noise.  That's why Noise Increases with Vehicle Speed.

At 30 mph, a typical auto may produce 62 decibels, about the noise of a human conversation. At 54 mph, the same auto would produce 72 decibels. Decibels are a logarithmic scale so an increase of 10 decibels is a doubling of noise.

California had an 85% rule.  The fastest 15% of drivers determines the new speed limit.  Over time, the speed limits on urban arterials climbed from 35 to 40 to 45.  This has been a disaster for road safety for people outside of cars.  It's also made cities noisier.

What can you do about road noise?
  • Reduce the number of cars.  Pedestrians and bicyclists are mostly silent.
  • Lower speed limits and enforce them.
  • Reduce vehicle sizes with sticks and carrots.  People are using cars much too big for their daily needs. (They can rent larger vehicles as needed.)
  • Increase the distance between noise generators and people.  
  • This and the next 2 figures are from this Traffic Noise Factsheet
  • Replace a car traffic lane with a protected bicycle lane and wider sidewalk. The bike lane protector is a low wall that protects the bicyclists from swerving automobiles and creates a noise shadow. A waist-high wall can make the stores & restaurants along arterials much quieter

Trees don't do anything to reduce noise, but they provide much-needed shade to counter the urban heat island effect.

Speaking of urban heat islands, ICEs produce a lot of heat.  Burn anything and it produces heat. Reducing the amount of ICEs on the streets, and making engines smaller would reduce urban heat, noise and air pollution and climate change.


1 comment:

  1. I'm always amazed how much quieter my car is when I get new tires. The county added rumble strips to the railroad crossing about 2 miles away and we can hear them quite clearly, SO glad I don't live closer. The trains were bad enough in town, but at least they were only every 20 minutes or so. And the noise level difference walking into work, vs. being outside at 10 am due to the interstate a mile away from work in Cedar Rapids was amazing. I can't imagine what it's like living in large cities with packed freeways.


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