Why is driving on the concrete parts of the highway so much louder than the blacktop parts? It is night and day different. All of a sudden you’ll switch from concrete to blacktop and realize how LOUD concrete roadways are.
In: Engineering
So the concrete makes that low *buzzing* sound due to the grooves cut in it. There are grooves cut about 3/4″ down causing your tyres to jump across and hit the next groove. There is actually a highway in California which, when you drive on it, sounds like the national anthem.the purpose of these grooves is to wake up driver when they’re dozing off.
I hope this helps
The groves is concrete also serve a as what is called control joints. Concrete does not give. It will crack. A control joint is a way to try and have a crack follow that line not a random one it chooses. These cracks do not take away from the strength of the concrete. Blacktop gives a little. It does not need control joints because it does not crack to the same extent as concrete.
One: while asphalt is compressed to make a nice smooth surface it is not nearly as dense as concrete is. Since concrete is much denser it does a better job of reflecting noise (hence why sound barriers on the sides of highways are made from concrete) which means that as your tires make noise when they drive over it more of that noise is being reflected back to you in the car.
Two: yes typically there are grooves cut into the concrete however when they are cut into the actual driving lane their purpose is to drain water away so your tires have more grip in wet conditions but in dry conditions it’s a channel that will echo the sound your tires make driving over the concrete. Those groove are not used in asphalt because the asphalt will absorb more water and there are a lot of nooks and crannies for water to drain away too
Black top has tiny cavities inbetween the grain on the surface. The size of these cavities is engineered by picking the right grain size. It’s not entirely random. Anyway, the cavitie’s job is to absorb sound. Ever been in a lecture hall and noticed these fancy holey drywall panels on the ceiling or the back wall of the room? the hole’s size, pattern and distance are designed to absorb sound and muffle reflections / echoes.
Concrete on the other hand is, well, concrete. Its job is to be cheap and reliable. No sound absorbing engineering in concrete.
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