Any driver who buys a quality audio system wants to enjoy their favorite music without being disturbed by road noise outside or the vibrations produced by the tires and engine. It would not hurt to soundproof your car with soundproofing material, get rid of all noises, and enjoy the peace and quiet. Soundproofing your car promises to greatly reduce the vibrations and noises of the road while driving. It allows you to enjoy the maximum performance of the car’s engine and system without annoying noises.
Also, no one wants to own a vehicle that sounds like a washing machine when driving. We’ve set up this guide to help you choose the soundproof products that suit your car, letting you know the main selection parameters, answering the so often-asked question – “Where can I find car soundproofing products at good prices?”
Is it worth to isolate your car?
Sound insulation is recommended for all vehicles. Even if it is a premium class car, for example, Audi A6, A8, BMW 5 Series, Ford Mondeo, etc. or a lower class car: all vehicles may require additional soundproofing in order to be quiet and comfortable on a long trip.
Many people say that soundproofing a car is only important if you modify the car sound system. From my point of view, this is not true because besides the noise caused by the sound system there can also be various noises, vibrations in the door, board, etc.
Soundproofing is done to reduce external noise (engine, rolling – shock absorbers, tires, etc.) or to create a better “acoustic” environment for the audio system in the passenger compartment.
Sources of car noise
There can be many reasons why there is noise inside the car. The usual noises are from the:
- traffic
- wind when driving at high speeds
- road (can be because of used or loud tires)
- engine
- exhaust
- sound system when listening to music
Diesel engine vs gas engine soundproofing
Diesel
The diesel engine is louder than the gas engine! This is a known fact, but it depends on the car’s model, year, class, etc.. However, in general, diesel engines are louder than gas engines due to the mechanics (it works by compression, not sparks). Engine soundproofing tutorial will be presented in a later article.
Gas
Depending on the engine, it can be very quiet, but the old ones are still quite noisy especially when we talk about lower end (class A or B) automobiles like Ford Fiesta, Volkswagen Polo, Mazda 3, Ford Focus, etc. This is because, due to their low cost, details such as soundproofing are not paid attention to when they are produced. This is why there should be an extra reason for soundproofing your car: disturbing vibrations, loud music noises, weird noises in doors.
If there is no extra reason, I recommend soundproofing your car if it is old or you love silence. Also, if you have children, soundproofing can be a good idea. They can sleep in the back of the car without being disturbed by the road noise.
How to measure the sound level in my car?
I wondered this too. I wanted to do a before and after in order to see some actual results of my work. After a bit of research, I found that the easiest method to do this is with an iPhone or Android app that measures the sound level. Just search on the store a free app with “sonometer” or “sound level” keywords. Download and install it and measure the sound before and after soundproofing your car. I don’t have an iPhone but a Samsung S7 edge. See the attached print-screens for results. As I soundproofed all my car, I checked the road noise when driving. I placed my phone in the phone support and drove on the same road twice (once before soundproofing and one after). I think the results are pretty good, but if you don’t trust your phone’s microphone, you can always buy a sound level meter from Amazon.
Identifying the noise source
Car soundproofing is indeed a recommended method for noisy engines, but to be able to figure out what product we need, a more careful analysis of the whole vehicle is required. Otherwise, we do nothing but throw money out of the window.
For example, if the noise that bothers you while driving is the result of the outside wind, you can try to close the window to see if the noise disappears. If you can still hear the noise, you know the problem (the source of the noise) is inside the car.
Tires can be another source of loud noise inside the car. That is because each company uses different materials to produce them based on their own technologies. So if you use a pair of worn tires that produce a loud sound, you can replace them with new ones. This is one of the most effective methods for eliminating unwanted noise. This is a perfect example where there is no need for a soundproofing product. Sometimes replacing or repairing a component of the car can eliminate the disturbing noise.
Typology of soundproofing materials
There are currently many types of soundproofing materials on the market even if they all serve the same purpose. Thus, you have to choose between rubber, spray, foam, and foil.
Soundproofing rubber
If you are an easy-going person who does not want to make a lot of effort on the car to soundproof it I recommend rubber because it usually has a soft-touch part for easy application on the vehicle panels. The major advantage of this material is that it transforms sound energy into heat, reducing its frequency. But, like any product, it also has a disadvantage: it emits an unpleasant odor, like tar or carbon monoxide, if it gets hot or burned. It depends on your climate, but, if the summer is hot, it can be unpleasant when you leave your car in the sun for a couple hours.
Soundproofing spray
The big advantage of the spray is that it does not have to be installed like other materials, you only need a paint gun and a compressor. It is sufficient to apply it to the interior surfaces, responsible for vibrations and noise during driving. It often comes bottled in aerosol tubes.
Soundproofing foam
Formed by compressing gas in the solid-state, the foam is ideal because it disperses the sound energy and vibrations to create a better “acoustic enclosure” for the audio system. It also applies to the side doors, greatly reducing the noise that bothers you. However, it doesn’t mean that it blocks the sound because it does not have such properties. Compared to other materials, it absorbs water, so either use a closed-cell foam or turn to a vapor barrier.
Soundproofing foil
Soundproofing foils are made of thick fibers that absorb sound. They are installed under the carpet of the car. Although it does not offer such a high performance as the already mentioned materials, when it comes to blocking the noise, it offers extra comfort. Most of foils are made of fibers or micro-fibers.
Working area
In choosing auto-insulating products, it is also great advice to keep in mind the area you want to soundproof. This is important because once applied on certain components of the car, these materials contribute to the increase in the mass of the car assembly, car inertia, and stiffness.
If you have opted for bituminous materials, you should remove the door panels to give them access. Because their application requires the use of an adhesive, it sanitizes the metal door of the doors with acetone to ensure that the sound-absorbing products are properly installed. Thus, vibrations are easier to control and transform into low-intensity heat. Many reviews of car soundproofing recommend that to improve acoustic properties, such a rug should be installed in the engine compartment.
If you have identified the floor of the car as the noise source, you don’t have to think very much as the soundproof foils are best suited for this operation. In this situation, it is necessary to correctly measure the door panels and the entire lower surface of the car so that the insulation is cut according to the desired measurements. Subsequently, remove the chairs, panels, and flooring from the floor, clean all areas with acetone for optimal application of the adhesive, including non-corrosive materials.
The use of soundproof foam is recommended in open areas, while for silencing difficult or irregular surfaces such as doors or engine compartment, you can choose to use the spray, as, as I have already said, the use of another type of material can add too much weight to the car components.
Brand of soundproofing material
Any user who has decided to buy a car soundproof material wants a high-quality product from which they can squeeze the last fraction of decibels. You will like to get rid of or at least significantly reduce the unpleasant outside noise produced by the engine, tires, or other sources. Once you will get used to driving a soundproofed car, you won’t stand another one.
If you have a generous budget, one of the best alternatives is Dynamat. The soundproof materials offered by this brand are part of the premium range, guaranteeing clear and deep sound inside the car by eliminating external noise and minimizing vibrations.
For those who are not willing to take a lot of money out of pocket, there are other brands like Noico. Perhaps the yield will not be as good, but by spending the same amount of money, you will have the opportunity to soundproof a two-fold surface. Customers’ preferences include STP and Noise Protection, other recognized manufacturers in this segment.
On the Internet, you’ll always find the right accessories for your car’s acoustic control, often even discounts or promotions, so many users prefer to buy online. According to their opinion, this is the best place to find a car sound at a good price.
Areas of application for insonorization
From the point of view of the noise zones, it seems that the greatest noise reduction is due to the sounding of the floor (and of the central tunnel and of the exit zone) then of the engine compartment towards the passenger compartment and its bonnet , wheel pots, side doors, side panels that are not part of the openings (ie not from the doors), and finally the luggage compartment including the luggage compartment door. If you want and there are resources available, you can also insulate the cabin ceiling.
If the tuning is aimed at improving the sound of the audio system, the doors and the trunk are the priority.
Soundproofing products
In terms of insulating products, they are classified into several categories: bituminous (or rubber-based) foils, paints for brush, paint spray or spray, soundproof foam, and sound foam insulators. Good results are obtained by combining several methods, not the use of one.
Bituminous or rubber-based rubber (Styrene-Butadiene-based on Dynamat) is of a self-adhesive type, with or without aluminum foil on the non-adhesive side (for superior heat resistance and thus use in the engine compartment). The mentioned workings of these films are absorbing the vibrations in the panel and transforming them into heat – mentioned in the dynamite – or simply by decreasing the resonant frequency of the panel.
These bituminous sheets also add weight to the panel, reducing its tendency to vibrate (especially useful for doors, behind the door faces). Of the specialized ones found in the markets, I found out just the dynamite and insufferable films from Sprint2000. But there are cheaper alternatives.
Thus, the aluminum foil Alu-Band foil (from DenBraven) is not based on Styrene-Butadiene rubber but bitumen and asphalt. The latter is used to insulate roofs, but essentially these films have the same composition as the specialized ones only incorporate more asphalt for waterproofing and are cheaper (about 5 times), but have an efficiency of about 2 times lower than the specialized sheets. If the carpet is placed immediately over these sheets, it is advisable to give the sheets a piece of powder (talc, etc.), so that if these sheets of the curtain do not stick to the carpet.
These foils are applied on the sheet in the area that is to be insulated, and, for higher adhesion, they can be pre-heated (in the sun, with the flame lamp, with the hot air blower). It is also useful to grasp the support surface (sheet) – either with a hot air gun, foehn, or the sun.
Greater than rubber / bitumen paint, they should be used in areas that are more difficult to insulate in another way, or where adding additional materials would add too much weight to the panel. Usually used for irregular doors and debris. They are also suitable for large panels (floor, ceiling) but tend to dirty and require proper protection of the windows and the interior of the car (dashboard, etc.).
Sponge-type, simple, or self-adhesive foam insulators disperse vibrations by reducing energy. These must be of the “soft” type with large cells, in order not to have a tendency to vibrate.
Extruded polystyrene insulating boards also have the ability to reduce noise but have less use in cars and especially in areas requiring rigidity (driver pedal or passenger pedal).
Foam soundproofing. To reduce the vibrations between different sheet metal panels, polyurethane foam can be used with brillium, which, when expanded, fills the voids. They can also be used to round the sharp corners, to back pots to the rims of the engine bonnet, to the body pillars (front, middle, rear), etc.
Caution: Commercial polyurethane building foams tend to absorb water over a long period of time. Their use in less ventilated areas (eg thresholds) can lead to the retention of humidity in the area and the amplification of sheet oxidation processes
Soundproof materials. In my opinion, the most efficient (and inexpensive), especially if used together with bituminous foils, are placed under the carpet. Apart from sound insulation, they also have a good result as thermal insulation.
Carpets. Although it may not seem so, carpets play an important role in soundproofing. Some time ago, for additional sound insulation, two carpet layers were fitted to the machine (original from factory). Preferably the carpet is on a rubber base (have a higher sound absorption degree).
Other non-insulating foils. Other types of insulating films, such as parquet floors, can be used successfully.
Considerations on areas of soundproofing:
Engine compartment
Generally in the engine compartment, there is the bonnet and bonnet between the engine compartment and the passenger compartment.
The hood’s insufflator has the role of reducing the out-of-air noise, it also has a small role in producing slow engine warm-up (sudden temperature variations do not do well for the paint) and a certain role to stiffen the hood, eliminating its vibrations due largely to its weight.
The engine and passenger compartment engine sensor, the engine compartment, only acts as a sunblock.
Interior
The sensor in the passenger compartment is mostly on the floor, on the common wall with the engine compartment (including under the dashboard), the bituminous foil in the door, and the vibration frames of the poles. Generally, lately it is a sponge type that has replaced the floor in the automotive industry in this area, but it would also be useful to apply a layer of bituminous foil under these insufferable / pastel sponges.
In Renault Megane 2, for example, this sponge has about 6-8 cm after my eyepoint estimate (thick). The bituminous sheets applied on the inside of the door faces help to reduce their vibrations, to make noise from the outside noise, and to increase the weight of the doors, which leads to a more pleasant closing. Especially useful for improving door speaker parameters.
Trunk
Given that the luggage in the boot is not so intense as it is transmitted in the passenger compartment (not for sedans and hatchbacks), I would recommend only the insulating with bituminous sheets, and less with other methods (pastel, maybe additional carpet) on the floor the luggage compartment and wheel pots as well as the inside of the rear wings. You should not ignore the trunk door, on which you can put bituminous foil, as well as pastel (as in Renault Laguna)
How to soundproof?
Here are the steps to soundproof a car door. I think this is the best way to learn how to soundproof your car if you are a novice. It will guide you through all principles of soundproofing, and then you can take it to the next level. Once I learned how to soundproof my car’s doors, I could very easily soundproof the rest of my car. These are the same rules you need to follow, and it’s best to start with the doors. So let’s go ahead. If you have any questions please leave a comment, and I will do my best to help you.
The tools required for soundproofing a car’s door:
– a cutter
– a metal roll
– a roller to press the material in hard-to-reach areas
– diluent – Before applying the soundproofing material, the surface must be degreased It is necessary to use a special thinner, not the one used for thinning the paint because it is much stronger it can destroy the wax or other impurities
– a paper towel roll
– soundproofing material
– ruler to measure the material
Car Door Soundproof Tutorial:
Here, the door panel must also be removed. So all the plastic elements must be taken apart until we get to the metal surface. The next step is to degrease the door with a diluent or acetone using the paper towels. Apply the acetone to the paper towels and rub the metal surface of the door. Usually, there may be a reinforcement bar for lateral impact, it’s like a pipe placed diagonally. When applying the material, you will not be able to pull the foil over that bar because there are places where you won’t be able to apply the material. If you try to do this, it will fill with water and will gather behind the soundproofing material. If this happens, it can destroy the metal, form rust, or degrade over time. If you do not have that diagonal bar, then you will have a horizontal one, and, if it does not make contact with the door, do not apply the material behind it!
You can search on youtube for: “[your_car] door panel removal”. Here is an example of how to remove the door panel on a Seat Leon (my car). I searched “Seat Leon door panel removal”. Most of the principles are the same on every car, so even if you don’t find your model you can follow this model:
Use the ruler to measure the distance from the top edge of the door to the reinforcement bar to see how much material you need. Then apply the material without covering the space (if any) behind the reinforcement bar. Use the metal roll to stretch the soundproof foil.
Certain materials require additional heating, while others can be applied only by pressing at ambient temperature. Make sure to check the material before trying to apply it to the door.
Most car soundproof foils have a pattern on the aluminum side. This will indicate when the material is stretched well on the surface. You can see stripes on it after stretching the material. If air bubbles remain, you can get rid of them by cutting the material with a cutter and then stretching it with the metal roll. If air is under the soundproof material it means that it does not have direct contact with the surface. If the material doesn’t make perfect contact with the surface it won’t soundproof good enough. Take care of the edges! Stretch the material well on the edges with a metal roll.
After you apply the material on the door you can put back the intermediate panel, attach the window to the crane, and isolate it. After fixing the intermediate panel and attaching the glass to the material, we will again go to the skim. When applying the material, we must take care of the holes where the clips through which the electrical cables pass.
After we have finished applying the material and the intermediate sheet, we will finish assembling parts, motorways, speakers, and the rest of the cables. I cut the material around the visiting holes and left the screws.
We then move to the front of the door. Remove the front door pocket and the speaker grille. On this, stick a sponge band between plastic and screws to prevent noise and vibration. In the back of my pocket, I put a sponge of 5 mm thick. On some doors, there is a padding material. Take it down and put an abrasive material along with the 5mm thick adhesive sponge to prevent direct contact between the plastic and the sheet and avoid unwanted noises. Before applying, do not forget to use the diluent.
After putting the adhesive sponge and the sun burning material, you can notice a major difference. No more noises can be heard when lightning the door panel. If the door elements screech or emit strange noises, you can use a 2mm thick tape that is placed on the edge of the components.
Conclusion
Hope this tutorial helped you to soundproof your car. There are simple steps which you can follow to reduce the road noise of your car, and you can do it at home in a few hours. I soundproofed my entire car in about 3 days (including the weekend) taking each individual part (doors, engine, floor) one at a time. Soundproofing your car greatly improves the comfort and the pleasure of driving, and I will do this with every car I will own. Even if the original soundproofing is ok, you will feel a big difference after you apply the extra layer.