How to reduce road noise in a car

When we talk about noise pollution from cars we rarely think about how to reduce noise inside the car.

We usually think about how noise generated by cars affects people on the outside, such as pedestrians or people in the “comfort” of their homes. This is definitely the bigger part of the problem. These people did nothing other than go about their lives, yet they can be deeply affected by the choices of others.

That being said, we live in a society where driving a car is the norm, and in many American cities it’s actually a must if you want to be able to do normal things, such as go to work, do groceries or visit the gym.

This means we are not only exposed to the noise made by cars when one passes us by on the street, but also when we ourselves are driving. For many, this means several hours per day, making it just as important to control how much noise we are exposed to inside our car, learn how to reduce the noise in the car, and how to soundproof the car, in order to make it more comfortable and healthy.

Where does the noise inside a car come from?

Cars start making noise the minute we turn them on. Unless you drive an electric car, there’s a combustion engine under the hood, which means thousands of explosions are taking place in your engine every second, even if the car is not moving.

Believe it or not, most of the noise we hear in our car does not come from the engine though.

Tire friction noises in the car

It is the friction between the tires and the road that produce the most noise.

You’ve probably noticed how sometimes the pavement changes suddenly while driving, and the noise inside your car changes completely. Sometimes it gets louder and sometimes it gets quieter, but what this comes to prove is that it’s in the contact between your car (that is, the tires) and the road where most of the noise is created.

This is the reason why noise-reducing asphalt has the potential to greatly improve the noise pollution from motor vehicles, and also why electric cars will not be the solution to traffic noise.

Mechanical noises in the car

Mechanical sounds are another important source of noise inside cars.

If you drive a relatively new car you probably won’t have this issue. But if your car is getting old and has significant miles on it, you might have started noticing mechanical noises while driving. These noises usually originate in the car’s suspensions, although they can also come from the drive belt or a part of the engine being slightly out of sync.

Another type of mechanical noise, which is not serious, but can be extremely annoying, is the one produced by the parts responsible for the interior finish of the car. These are things like the door of your glove compartment or the heating/AC vents. All these plastic pieces are designed to fit together, but when subject to repeated extreme temperature changes over time, these joins can start failing and producing small sounds that can become really irritating for the people inside the vehicle.

Aerodynamic turbulence noises in the car

The last family of noises we find inside cars comes from the turbulence created as the car advances through the air. Air is constantly hitting a car as it moves forward (or backward). The faster the car moves the “harder” this air hits it and the more turbulence it creates. As you might have already guessed, turbulence equals noise.

These turbulences tend to happen where the surface of the vehicle is not smooth, such as around the rearview mirrors, the door handles, and the edges of the windows.

Reducing road noise in your car

Now that we’ve covered the main sources of noise inside cars you probably have a better idea of which kind of noise is bothering your specifically. That’s the first step. Now let’s look at what you can do to reduce each type of noise inside your car.

Let’s keep in mind that the best way to reduce noise is always at its source. If we can prevent the noise from happening then we are done. If we can’t, then we’ll have to look for ways to mitigate that sound before it reaches the cabin of the car.

Reduce car noise from engine

Before we attempt to tackle engine noise ourselves, we need to make sure that our engine is in good health. You should always service your car regularly (as recommended by the manufacturer) and take it to the shop as soon as you notice anything out of the ordinary.

If you haven’t serviced your car in a while that will be the best place to start. Having a mechanic check it out and replace some parts that might have worn off over time might already be a big improvement.

If after making sure your engine is running smoothly you still feel it’s too noisy, you need to try to soundproof the cabin from the engine as much as possible. There are many types of soundproofing materials available on the market that will help reduce this noise, such as foams and mass-loaded vinyls.

These layers have to be installed around the engine bay. In many cases you will only be able to access the pedal area without having to disassemble a significant part of the dashboard. Try installing the sound-absorbent material there first, and if you notice an improvement consider looking for a professional who can install it in other less accessible parts.

Reduce road noise from tires

As already mentioned earlier, the friction between the tires and the road is by far the main source of noise generated by motor vehicles.

In order to ensure our tires are as quiet as possible, we first need to make sure they are in good shape. Even if the grooves on your tires look good, the rubber tires are made from tend to harden over time. So if your tires are over 2 years old, no matter how new they appear to be, it is possible that the rubber has started to decay and is producing more noise than the same tire would if it was brand new.

The next thing to check is tire pressure. You would not believe the difference having your tires properly inflated make. Look up the tire pressure recommended by the manufacturer and stick to that. Remember to check the pressures regularly, as even the best tires will tend to deflate slightly over time.

If you have good tires, inflated to the recommended pressure, and you still feel the noise they make is too loud, you can consider installing noise-absorbing wheel well liners. Wheel well liners are molded pieces that are placed from the outside of the car, around the area of the tires, to prevent, dirt, mud and water to enter the engine bay. That being said, because they are mounted so close to the wheels of the car, they can also help absorb noise from the tires and prevent it from getting inside the cockpit.

Reduce car noise from suspensions

No matter how good the road is, it is always going to have some amount of irregularities. These can be looked at at a large scale, like a hole in the road, or at a smaller scale, like the grain of the asphalt.

Regardless of the size of these irregularities, all vehicles are equipped with suspensions to help absorb them and reduce any discomfort to the cockpit. Without going into too many details, suspensions have a bunch of moving parts, shocks and springs, constantly working together to absorb these irregularities. All these parts have healthy amounts of oils and grease lubricating them, and over time it is possible that this lubrication starts to fade, opening the door to undesired noise.

If you notice the noise your car is making only happens when going over a speed bump, or when driving on a dirt road, it is very possible that this noise is suspension related.

To solve noises in your car coming from the suspensions, I recommend you visit a mechanic. In most cases they will be able to re-lubricate the right parts and get them back as new. Eventually though, you’ll need to replace your shocks, they don’t last forever.

Reduce car noise from windows

Windows are another weak spot of the car when it comes to isolating the cabin from outside noises.

Windows are moving parts that open and close, they rely on “soft” materials to seal those openings. Soft materials are more vulnerable to temperature changes, UV rays from the sun, salt in the air if you live near the sea, etc. In general, the softer the material the quicker it will lose its properties, and when they do, more noise will make it into your car’s cabin.

As in all the other cases, the first thing to do is make sure that our windows, including not only the glass but also the rubbers around it, foams, pads, etc. are in good shape, and replace the parts that aren’t.

If you still feel too much noise is making it through the windows, there are two things you can try.

The first is to install a transparent noise-reducing vynil on your windows. Some new cars already incorporate this kind of material in between the double safety glass. For those that don’t, you can add it to the outside of the window. This will help reduce the noise inside the car’s cabin by around 3dB. Not a lot, but you have to start somewhere!

The second thing you can do to reduce noise in your car coming from the window is to install wind deflectors. These plastic pieces which are mounted around the closing edges of the window might not be super sexy, but they will definitely help keep the interior of your car quieter.

In essence, a wind deflector will be pushing the turbulence generated as your car moves through the air further away from the window’s edge, where it is more vulnerable. When you hear the sound of the wind, that is in fact the noise of turbulence. Even when you blow out a candle, the air-flow noise you hear is small turbulence. So needless to say, the further away you can keep turbulence from the weaker spots of your car, the better.

Conclusion

Some of us spend long hours in our cars, commuting to work, driving the kids around, etc. And for those who work in delivery or transportation, the problem gets even worse.

By implementing the tips above, you can reduce road noise in a car and make your ride quieter and more comfortable. Although it may take some effort and expense to implement these solutions, the end result is well worth it.

Enjoy a smoother, quieter ride!