An extraneous sound coming from under the wheel arches can turn a trip even in a premium car into torture for hearing. Monotonous hum Or a whistle that grows with speed not only irritates the driver’s nervous system, but also masks other important sounds that signal suspension or transmission malfunctions. Often, car owners mistakenly believe that this is an inevitable fee for operating budget tires or the age of the car.
However, in most cases, the situation can be radically corrected if the source of vibration is correctly identified and the appropriate method of dealing with acoustic discomfort is chosen. Noise insulation of wheel arches It is one of the most effective ways to improve the comfort class of a vehicle, returning it to factory performance or even surpassing them. In this article, we will discuss in detail the physics of the process, the sources of sound and proven ways to eliminate them.
Before buying expensive materials, it is necessary to conduct a thorough diagnosis, since the fight against symptoms instead of the cause can lead to unnecessary costs. Acoustic comfort It depends on many factors: from the tread pattern to the state of the hub bearings. Understanding the nature of sound is the first and most important step to staying quiet in the cabin.
⚠️ Before starting noise insulation work, make sure that the source of noise is not a malfunction of the brake system or critical wear of suspension parts, as pasting arches can make it difficult to access them during emergency repairs.
The nature of the occurrence of acoustic discomfort
The sound, which we perceive as the hum of wheels, is a complex cocktail of mechanical vibrations and aerodynamic noise. The mechanical component is transmitted through the suspension elements directly to the body, causing the metal panels to resonate. The aerodynamic component occurs when the air flows around the rotating wheel and arch elements, creating swirls and whistles.
Particular attention should be paid to the condition of the road surface and the type of tires. Studded rubber In winter, it generates much more noise due to the contact of metal elements with asphalt than summer counterparts. In addition, worn tread or uneven wear ("hernia" or "saw-like" wear) create additional low-frequency vibrations that are difficult to drown out.
Also (cannot be ignored) resonant frequencies of the wheel arches themselves. The thin metal in this area of the car often works as a speaker membrane, amplifying any gravel strikes or airflow. That's why. vibrating Metal is the basic stage of work, without which the application of soft materials may be ineffective.
To better understand the sources of noise, consider the main factors in the table:
| Type of source | Nature of sound | Dependence on speed | Probable cause |
|---|---|---|---|
| Mechanical | Hood, howl, knock | Straight (grows with turnover) | Hub bearing, tire wear |
| Aerodynamic | Whistling, wind noise | Sharp rise after 80 km/h | Air swirls, dirty arches |
| Resonant | Freaking, echoing | Constant at certain frequencies | Vibration of metal arches, loose plastic |
Diagnostics: rubber, bearings or suspension?
Before starting to paste the arches, it is necessary to exclude technical malfunctions. Often drivers spend thousands of rubles on materials, when the problem lies in the banal. bearing-wear. To check, accelerate to the speed of noise and try to make a smooth maneuver of rearrangement. If the noise increases when you turn left, then the right side is loaded, and the problem is most likely in the right bearing, and vice versa.
A visual inspection of the tires can also provide answers. Uneven tread wear, often referred to as “spotted” wear, indicates problems with the collapse-divergence or condition of shock absorbers. Hard sidewall Some tire models (especially RunFlat) are themselves a source of increased noise that is transmitted to the body. In such cases, complete noise insulation may not give 100% of the result, and the only way out is to replace the set of rubber with a quieter one.
Check the plastic slats (lockers) as well. If they are poorly secured or have cracks, they will vibrate and rattle as they move, creating the illusion of noise from the wheels. Sometimes it is enough to simply tighten the mounts or replace the burst clips to eliminate the annoying sound. Keep in mind that the dirt and ice that sticks in the arches also change aerodynamics and can be a source of noise.
☑️ Diagnostics before noise insulation
Selection of materials: vibration insulation against noise insulation
Many motorists confuse the two concepts, although the physics of the process is fundamentally different. Vibrational insulation (vibrodamper) are heavy bitumen-polymer or mastic materials with aluminum coating, whose task is to quench the vibrations of the metal, turning mechanical energy into thermal energy. Without a high-quality vibrodampfera, applying any other materials to the wheel arches is almost meaningless.
Noise insulation (sound absorber) are light porous materials (feel, foamed polyethylene, melamine) that absorb the air wave of sound, preventing it from penetrating the cabin. Combination materialsFoil, such as foil noise, works worse than specialized solutions, as the foil in this case works as a reflector of heat, not sound, and can even create resonance.
For wheel arches, moisture resistance is also critical. The use of materials that absorb moisture (for example, ordinary felt without protection), will lead to the fact that after a couple of months in the arches will begin to accumulate water, causing corrosion of metal and the appearance of an unpleasant odor. Modern materials based on synthetic felt or closed-cell foam are deprived of this drawback.
The secret of layering
Why is one layer not enough? The effect is achieved due to the difference in the density of materials. Heavy vibrodempfer quenches low frequencies (hum), and a light porous layer absorbs medium and high frequencies (noise spikes, gravel). The mono-layer cannot cover the entire spectrum of sounds.
Technology of processing wheel arches from the outside
The treatment of the outer part of the arches requires the utmost care, as the materials will be exposed to aggressive effects of sand, stones, reagents and water. The first step is always a quality washing and degreasing of the surface. Any dust or oil film will reduce the adhesion of the vibrodampfera, and over time it will simply fall off along with pieces of dirt.
A layer is applied to the purified metal vibrodempher. It is important to warm up the material with a building hair dryer to a temperature of 40-50 degrees and carefully roll it with a solid roller, expelling all air bubbles. It is not necessary to seal 100% of the surface, it is enough to cover 70-80% of the area, paying special attention to the central parts of the metal panels, where the amplitude of the vibrations is maximum.
On top of the vibration insulation, it is recommended to apply a layer of liquid noise insulation or anti-gravel with noise-absorbing properties. This will create an additional barrier to the impact of gravel. Liquid rubber It seals the joints well, but may require updating over time. If you use solid plastic lockers, their inner side is also worth pasting with vibration and noise materials.
⚠️ Warning: When heating metal with a hairdryer, be careful with plastic cells, fuel tubes and wiring located in the arches – they can be easily melted or damaged by high temperature.
Internal treatment and protection of the salon
If the car design provides access to the inner part of the arch (often through the removal of the underwing or from the cabin), this stage should not be missed. It is through the inner cavity that the sound often penetrates the cabin most intensively. There's also a bundle here. vibrodamper + noise absorber.
For the interior of the arches, it is better to use foil-based materials as the first layer, since they have water-repellent properties. The second layer should be made of a moisture-resistant noise absorber, for example, based on synthetic felt or closed-cell polyethylene. The usual foam here will quickly collapse from moisture.
Pay special attention to the junction of the arch and salon. Often, noise goes through the technological holes through which the wiring or cables pass. They must be carefully sealed. vibromastics Or special plugs. High-quality processing of the interior of the arches can reduce the overall noise level in the cabin by 3-5 dB, which subjectively feels like a significant improvement in comfort.
Use anti-scrap (madeline) for pasting the edges of plastic underwings in places where they come into contact with the body. This will eliminate rattling of plastic on road bumps, which is often confused with tyre noise.
Comparison of methods and expected effect
The result of noise insulation directly depends on the quality of the materials used and compliance with the technology. Cheap analogues of the vibrodumpfer, which remain sticky and fluid even after rolling, do not work - they only weigh down the design. The high-quality material after polymerization (cooling) should be converted into an elastic plate.
Don’t expect complete silence like in a studio recording, especially on studded rubber. Physics is physics: thorns knock on asphalt. However, acoustic comfort This will increase due to the fact that the low-frequency hum is transformed into less noticeable background noise, and the rattling of the panels will disappear completely. The passengers in the back seat will appreciate it first.
If the car has poor noise insulation of the floor or doors, then processing only the arches will give only a partial effect. However, it is the arches that are the main source of noise at speeds above 60 km / h, so work with them is most noticeable.
High-quality noise insulation of arches reduces the overall noise level in the cabin by 3-5 dB, which is subjectively perceived as a two-fold decrease in the volume of extraneous sounds.
Frequently Asked Questions (FAQ)
Do I need to remove the wheels for high-quality noise insulation?
Removing the wheels is a mandatory step. This provides access to the entire surface of the arch, allows high-quality washing and degreasing of metal, as well as safe operation of a construction hair dryer and roller in all hard-to-reach places.
Can you use conventional construction noise insulation for your car?
It's not recommended. Building materials (e.g. foam) do not have the necessary heat resistance and can melt or release toxins when heated from the exhaust system or engine. In addition, they do not have the necessary density and adhesion for car vibrations.
How long will it take to process one arch?
With experience and a ready set of tools, the processing of one wheel arch (external and internal parts) takes from 1 to 2 hours. This time includes washing, drying, degreasing, cutting materials, heating, rolling and assembly.
Will the noise insulation help if the bearing buzzes?
No, noise insulation will only mute the sound of a faulty bearing a little, but it will not eliminate the cause. Moreover, the hum of the bearing may be enhanced due to changes in resonant frequencies. First, you need to replace the faulty part, and only then deal with acoustic comfort.