
resonance issue refers to the phenomenon where prolonged use leads to high-temperature fatigue and aging of the rubber in the engine mounts, which can easily cause resonance. In severe cases, it may also produce bumping and friction noises; other causes include engine misfire, deformation of the engine guard plate, or improper installation. If a car experiences engine resonance problems, it is necessary to take it to a 4S shop as soon as possible for a comprehensive inspection and adjustment. Engine resonance involves comprehensive issues such as components, joint processing, and tuning, so it is recommended to conduct an inspection and repair promptly. Taking the Volvo XC60 2021 T5 AWD Inscription version as an example: it is a mid-size 5-door 5-seat SUV with a length, width, and height of 4688mm, 1902mm, and 1658mm respectively, a wheelbase of 2865mm, and is equipped with an 8-speed automatic transmission.

I drive a 2019 S90 and discovered an issue within a month of taking delivery. At highway speeds, there's always a buzzing sound in the cabin that's particularly uncomfortable for the ears, similar to the pressure felt during airplane takeoff and landing. After driving just 40 minutes home from work, I'd feel dizzy and nauseous. Later I learned this issue is called the 'resonance gate,' reported by many Volvo owners. The main problem lies in the exhaust system design - at specific RPMs during exhaust emission, it generates low-frequency noise that resonates with the cabin space. The manufacturer later introduced two solutions: one was installing damping blocks to reduce vibration amplitude, the other was upgrading the exhaust valve control program. I chose the latter - the dealership flashed the ECU for free, which alleviated about 70-80% of the symptoms. The key is to address it early.

Having followed the resonance issue for two years, this problem is essentially a design flaw in the vehicle's NVH (Noise, Vibration, and Harshness) control. When the engine operates between 1800-2000 RPM, the exhaust sound wave frequency drops to around 20Hz, a range that is less perceptible to the human ear but can cause eardrum resonance through bone conduction. Particularly in models like the XC60, where the trunk is directly connected to the cabin, sound wave reflections amplify the sense of pressure. Interestingly, individuals with lighter body weight are more likely to perceive it, as their internal organ resonance frequencies happen to fall within the low-frequency range. The manufacturer's ultimate solutions focus on exhaust system improvements: either installing Helmholtz resonators in the mufflers to absorb specific frequencies or using active noise cancellation technology to generate opposing sound waves for cancellation.

Last year, while helping my neighbor inspect his used XC60, I encountered the resonance issue. Once on the road, there was a noticeable pressure on the eardrums, and the plastic parts on the dashboard vibrated along. This low-frequency noise couldn't be detected with a regular decibel meter; a frequency analyzer was needed. The investigation revealed that the issue was with the angle of the exhaust tailpipe—the original design caused airflow to form vortices at specific RPMs. We tried three makeshift solutions: adding soundproofing foam in the trunk had limited effect; welding exhaust hangers reduced vibrations but damaged the car; the most effective solution was replacing the tail section with an aftermarket exhaust with a valve, costing over 3,000 yuan but providing a permanent fix. I recommend fellow car owners to first check if the exhaust system's rubber hangers have aged—replacing this small part costs only about 200 yuan.

As an automotive journalist, I covered the entire resonance gate incident. It began with collective complaints from 2017 S90 owners, with symptoms mainly manifesting as persistent low-frequency noise during steady driving at 30-50 km/h. The manufacturer initially dismissed it as 'isolated cases' until China's General Administration of Quality Supervision intervened in 2020, prompting a recall. The core issues were defects in the exhaust system's acoustic design and overlapping resonance points in the body structure. Ironically, the Lynk & Co 09, built on the same platform, didn't have this problem because it included two additional resonator chambers in the exhaust system. The incident had two major consequences for Volvo: first, electronic exhaust valves became standard across all models post-2021, and second, the brand's used car depreciation rate became 15% higher than competitors.

Over 300 members in our car enthusiasts group have been troubled by the resonance issue. Some described it as feeling like their head was stuffed into a fish tank, and a pregnant owner was forced to sell her car due to long-term tinnitus. From an perspective, the main contradictions lie in two aspects: first, the SPA platform, in pursuit of lightweight design, set the body resonance frequency at 17-22Hz, which happens to fall within the infrasound range most sensitive to human ears; second, Volvo's environmental philosophy led to the exhaust pipe diameter being too narrow, causing excessive airflow velocity and triggering standing waves. The group has summarized cost-effective solutions: first, use sealing strips to close the gaps in the trunk lid (costing about 30 yuan), and if that doesn't work, add an electric intake valve (around 1500 yuan). If all else fails, the only option is to replace the exhaust pipe with one equipped with dynamic damping, which requires a budget of five to six thousand yuan.


