What to Do About Severe Low-Frequency Noise After Soundproofing the Four Doors?

[VonHarrison]

You can add a layer of automotive interior sound-absorbing cotton to the areas that have been treated. Apply an advanced sound-absorbing foam acoustic material under the hood, which can both absorb and dissipate a significant amount of engine noise and also suppress hood vibrations.

[JosiahMarie]

I've encountered a similar issue before. Last time when I did the four-door soundproofing myself, I experienced a constant buzzing sound while driving. After extensive troubleshooting, I found that the damping sheets were applied too densely – covering the entire inner door panel actually amplified low-frequency vibrations. I had to remove the door panels again, cut the damping sheets into palm-width strips, and applied them in a crisscross pattern with gaps between each piece. Then I added several layers of acoustic foam between the metal door panel and interior trim, specifically choosing that black wave-shaped foam designed to absorb low frequencies. Finally, I replaced all four door seals with new ones to prevent sound leakage. After these modifications, the ear pressure sensation disappeared completely. You might want to try adjusting material distribution and adding more sound-absorbing layers – it should help. Remember, effective soundproofing isn't just about piling on materials; the placement and combination are crucial.

[SanRosalie]

Bro, you're not soundproofing, you're installing a subwoofer! I was tortured by this issue for half a month. The key is to check a few aspects: whether the damping sheets are applied as thick as pancakes, which can actually amplify low frequencies; whether the wiring harness inside the door is securely fastened, as loose wiring can also cause resonance; and whether the door trim panel clips have become loose from disassembly. My solution was to tear off most of the inner damping sheets and replace them with a grid-like application, then stuff three layers of sound-absorbing cotton. Don't forget to keep the drainage holes at the bottom of the door clear, otherwise, the sound will bounce around in the sealed space. After doing all this and driving for two more weeks, it feels much better.

[OZoey]

To address low-frequency issues, targeted solutions are essential. First, inspect whether the soundproofing material inside the door is properly compacted without air gaps, as voids can create a drum effect. If using a full sheet of damping material, consider switching to strip-shaped damping panels, preferably about five centimeters wide, applied in a crisscross pattern. Second, install professional sound-absorbing foam between the door panel and trim, especially melamine foam with high low-frequency absorption. Don’t forget to check if the door seals are aged or leaking air. If the problem persists, it may stem from other areas like the chassis lacking soundproofing, leading to low-frequency buildup—consider adding trunk insulation to disperse sound energy. In severe cases, examine whether the speaker gasket sealing is the culprit.