Road noise is one of the most complained-about noises in the United States. Whether you are sick of listening to cars driving down your street all night or you hate hearing the “thud” of concrete while on the road yourself, there is a solution for quieter roads. Understand why roads are loud and how asphalt pavement can reduce noise in the safest, most cost-efficient way possible.
What Causes Road Noise?
Most of the car noise that you hear is simply the interaction between the road and the car’s tires. The more texture that either has adds to the noise. You can visualize this by clapping your hands. The impact creates a loud sound, right?
The same thing happens on the road because the trapped air on the pavement gets forced out due to the pressure of the wheels hitting the ground. The more displacement there is on the road, the more chances there are to trap air and create noise.
When you are off-roading, the noise is much louder because of the gravel and texture of the ground. Your vehicle runs over all those little rocks and forces out the air. It might seem obvious that the smoother the road is, the quieter the noise becomes. While this can be true, building a flat, non-textured road is a big mistake! Without a little displacement, friction doesn’t happen. Low friction can compromise braking distance and can become a serious safety problem.
Roughness on the road allows cars to stop quickly and efficiently, so cutting out texture is not the solution. Instead, consider how different types of road affect noise.
Overall, there are two common types of pavement: rigid and flexible. In fact, nearly 70 percent of all U.S. roads are paved with one of these two types of pavement. When deciding which is more cost-effective and practical, road noise undeniably is a factor.
- Rigid Pavement: This type of pavement uses cement concrete to provide a stiffer foundation. It has a high flexural strength. Rigid pavement is often used for parking lots due to its sturdiness, but cracks or damage in concrete can be permanent. Concrete can also be very loud because the rigid pavement doesn’t absorb sound.
- Flexible Pavement: This type of pavement is made with bituminous (asphalt) materials that absorb noise. As a result of the multiple layers of material, the road can better cope with the stress of heavy loads. This pavement is flexible because it bends or deflects the weight of vehicles that drive over it. Along with reducing sound, absorbent asphalt provides drainage and decreases the amount of standing water on any given road. These types of roads also expand and contract with temperature fluctuations, making them resilient to temperature changes. You can save time and stress as well because cracks and damage are fixed easily. While maintenance on flexible pavement can tend to be more expensive than on rigid cement, the overall cost of flexible pavement is much lower.
Is Quiet Asphalt Really a Thing?
You may realize the benefits of flexible paving, but can it really reduce noise on the road? The answer is yes! Because of the many layers, asphalt is not smooth. There is plenty of texture to allow for safe braking, but it is still much quieter than normal cement. It doesn’t compromise any friction, yet it is noticeably quieter than rigid pavement.
Why? Asphalt is extremely porous. By absorbing the air and vibrations from under the tires, the porosity of this pavement reduces sound by 3 to 5 decibels, which is enough to profoundly the diminish the volume of noise.
Flexible pavement is more effective in lowering noise than barrier walls. These walls are built to stop the bulk of sound from reaching buildings and even residences. However, they are not as efficient and they don’t do any good for roads without barrier walls. They also cost more than paving asphalt.
The usefulness of asphalt is becoming increasingly better-known both within the nation and around the world. The flexibility of this type of pavement allows noises to be reduced while still providing a safe allowance of friction for cars to brake.
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