Has the Low-Frequency Resonance Issue in the 2021 Volvo Been Resolved?
3 Answers
Volvo's solution for low-frequency resonance involves installing high-efficiency soundproofing cotton to reduce noise. Below is an introduction to low-frequency resonance: Low-frequency resonance occurs when sound waves transmitted through the air reflect off the car body, creating resonance. Certain frequencies of reflected sound waves align with the original sound waves in vibration direction, amplifying those frequencies. Conversely, other frequencies may cancel out when the reflected waves oppose the original waves. Noise frequency: Since low-frequency vibrations and noise frequencies are close to those of human organs, they can cause resonance, significantly impacting internal organs. Prolonged exposure may lead to irreversible damage to the heart, lungs, spleen, kidneys, etc. Sensitive individuals may experience headaches, palpitations, or mental fog, with long-term effects on mental health.
When I was driving the 2021 S90, I did suffer from low-frequency resonance headaches. Later, in the car owners' group, I learned a few tricks: I went to the 4S store for a free upgrade of the rear tailgate hydraulic rod buffer block, which was the manufacturer's solution to the resonance issue. I laid 3cm of wave soundproofing cotton in the trunk myself, especially adding two extra layers of vibration damping pads in the spare tire well. The most effective solution was replacing the engine mount bushings with an improved version, which reduced vibration transmission by half. Now, my ears don't feel stuffy on the highway. The car's sound insulation was already good, and after solving the resonance issue, it's even more comfortable than my friend's newly purchased car.
Last year, we handled over ten cases of resonance issues with the 2021 model, focusing on three key areas: First, loosen the tailgate latch screws by two turns to reduce the impact noise when closing the door. Second, adding sound-absorbing material inside the rear wheel arch liners is most effective—our shop uses 3M's AN050 material. The most crucial step is filling the cavity with foam sealant at the beam frame under the rear seats. Currently, the manufacturer has released a 2.0 version of the ECU program specifically targeting idle resonance. After the upgrade, steering wheel vibrations at 800 RPM idle speed are significantly reduced. We recommend addressing all three points simultaneously.
