Where Should I Start?
You need to contend with both the airborne noise created by the engine itself and the vibration that it sends through the structure of the car and it’s sheet panels. Engine noise can enter your cabin on some key places such as the doors, the firewall, and the windshield.Doors
Most cars have doors with very minimal insulation – just two sheet panels with an empty space inside for the window mechanism. It’s commonly one of the less insulated areas in the whole car. So, if you want to know how to reduce engine noise in car cabin, insulating your front doors will have a fair impact on the volume of engine noise that goes inside your cabin. Doors are one of the simpler areas to work on, as you just need to remove the door cards to access its interior. Hence being the best place for a beginner to start the sound-deadening process. Butyl rubber mats are the most effective way to kill sheet panel vibration noises and also to block airborne sound from the exterior.- After a good cleaning, we start by sticking those butyl mats to the outer door sheet, ensuring to cover as much of the door as possible with insulation, while taking care to avoid obstructing any moving parts such as the lock or window mechanisms.
- To achieve optimal results, we also cover with butyl rubber mats the internal door sheet and the holes for accessing the window mechanism. This way we attain a great barrier for the airborne noise inside the door, blocking it to enter the cabin.
- We end the process by applying sound-absorbing foam at the top of the butyl layer. This will absorb interior airborne sound waves, reducing echoes and high-pitched frequencies and will also act as a bed for the door card, muffling all kinds of rattles and giving it a more solid consistency.
This easy-to-do process, will not only contribute to reducing engine noise in the cabin but will also improve dramatically your car’s stereo sound quality and grant a solid and upmarket door-shut sound.Firewall
A vehicle firewall is what separates the engine compartment from the cabin. As you may expect, it plays a key role as a sound barrier. Improving its noise-blocking capabilities will contribute to a quieter engine inside the cabin, giving the feeling that it’s placed far away from the passengers. It will also help as a heat-blocker, keeping the cabin cooler.Firewall access is often tricky. You can have access to a big portion from under the dashboard, removing just the glove-box and the bottom panels and pushing away the carpet, but for complete and easy access, you should go to the process of removing the entire dashboard as well as the front section of the car carpet.
- After a good cleaning, start by sticking butyl rubber mats everywhere you have sheet metal exposed. Usually, you’ll have to lift or even completely remove the already existent factory insulation mat to access the metal underneath.
- After covering all the metal, apply a layer of mass loaded vinyl (MLV), checking if there is still some free space where the material may fit (looking forward not to obstruct pedal movement or interior trim mounting points). MLV is available in different thicknesses to fit most areas.
Windshield
Unfortunately, you can’t sound-insulate your windshield. For that, this last step will help you on how to reduce engine noise coming through it. Most engine noise entering the cabin through the windshield comes from the engine compartment through the hood and that is just what needs to be sound-insulated. Not only to stop sheet panel vibrations but also to block airborne noise inside the engine compartment to escape from the outside through the hood.- If your car already has a hood insulation pad, carefully remove it and deep-clean all the metal inside.
- Stick a layer of butyl rubber mats to the sheet metal, ensuring to cover as much area as possible to both kill the vibrations and also to build a sound barrier where the sound waves can’t travel through.
- Place the original manufacturer insulation pad on its place or in the case your car doesn’t feature one, apply a layer of a specific heat-resistant pad with sound damping material, with a reflective aluminum sheet covering it on both sides.
