Summary of the News in Plain Language
Residents of two buildings in Weifang, Shandong, have been troubled by a mysterious, low-frequency humming noise for a whole year. It was only when Zhu Lin, a doctor of mechanics known online as a “noise hunter,” stepped in that the source of the problem was discovered: slight vibrations in the walls on the second underground floor, which resonated with the interior spaces of the buildings, causing the strange phenomenon where the entire house would shake but the noise could not be located. After this video went viral, a previously invisible group of millions of victims came to light—countless people across the country are suffering from this constant humming noise that feels like having a drum covering their heads, with their beds constantly shaking, making it impossible to sleep and severely affecting their health. However, the vast majority of these people cannot find the source of the noise, nor do they have any legal means to seek relief. Zhu Lin helps people for free or for a cost equivalent to the materials used, receiving thousands of requests for assistance every day. His 35 support groups are all full, but he alone cannot handle them all. This issue exposes the shortcomings in building standards left over from the rapid development of the real estate industry over the past 20 years, as well as the gaps in existing noise detection and compensation systems. Moreover, the large-scale construction of AI data centers in the future could pose new threats of low-frequency noise.
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Detailed Analysis
Why is low-frequency noise considered a “ghost in the house”? Finding its source is more counterintuitive than solving a crime
The noises people usually encounter, such as from construction or square dancing, are obvious and can be traced to their source. However, low-frequency noise is like an invisible expert: it has a low frequency and long wavelength, so it does not travel much through the air. Instead, it travels through the steel beams, concrete walls, and floorboards of buildings, where its energy is hardly attenuated. This can lead to bizarre situations where the noise source is quiet, but the room several walls away is in chaos. For example, in the Heze case mentioned in the news, the actual problem was near the tiles in the bathroom. Standing in the bathroom, there was no sensation, but the bedroom, two rooms away, felt as if there was a roaring engine. Even worse, low-frequency noise can find “amplifiers.” For instance, a slight vibration from a motor several kilometers away can be amplified by a 1-centimeter gap between a cabinet and a wall, turning the noise into a bothersome hum that the owner might not even suspect is caused by that cabinet.
Why has the problem of low-frequency noise suddenly become more widespread in recent years? It’s not that it didn’t exist before; it was just hidden
Many wonder why they didn’t encounter this problem when they lived in older buildings as children. This is a result of the rapid development of China’s real estate industry over the past 20 years. Back then, to speed up construction, the standards for residential floor impacts were relaxed to 85 decibels, and the buildings were made thinner without additional shock-absorbing layers. The pumps, elevators, and transformers installed in the buildings also lacked proper shock absorption. Now, these buildings are reaching the end of their 15-20-year service life, and their components are starting to fail, emitting low-frequency vibrations. Additionally, people no longer rely on moving to avoid such problems. During the housing boom, many simply sold their homes and moved, but with the current stable housing market, the cost of moving is too high, exposing these previously hidden issues. The problem is not limited to homes; cars can also be affected. For example, the “resonance issue” with Volvo cars was a well-known example.
Why do so many people suffer from low-frequency noise? It’s because people’s sensitivity to it varies greatly
Some people experience discomfort or even tinnitus at 20 hertz, while their family members may not notice anything at 200 hertz. As a result, the victims are often labeled as being “overly sensitive or experiencing hallucinations due to stress,” suffering additional injustices.
Why has the problem of low-frequency noise become more prominent recently? It’s because it was previously hidden
Many people wonder why they didn’t hear about this issue in older buildings. This is due to a cumulative effect over time. The first wave of the problem came from the rapid construction during the past 20 years. To speed up construction, the standards for residential floor impacts were lowered, and the equipment (pumps, elevators, transformers, etc.) was not properly designed to absorb vibrations. Now, as these systems age, they begin to emit low-frequency noise. The second wave is due to the fact that people no longer rely on moving to avoid such issues. In the past, buying a new home was a common solution, but with the current housing market’s stability, the cost of moving is too high, exposing these problems. Low-frequency noise is also a problem in cars; for example, the “resonance issue” with Volvo cars was a well-known example.
Why do victims of low-frequency noise face so many obstacles in seeking relief?
Victims face numerous barriers in trying to get help. When they contact the property management or regular testing agencies, conventional decibel meters cannot detect the problem because the noise is within the walls, and the decibel levels in the air meet the standards. Most third-party testing agencies only issue reports that comply with national standards, avoiding responsibility for identifying the source of the noise. Legal proceedings are even more difficult; if the testing is scheduled but the noise stops due to a temporary issue (like a broken pump), the responsibility is unclear. The costs of professional judicial evaluations are prohibitive for most families.
Why can’t Zhu Lin help everyone? The industry is still in its infancy
Zhu Lin’s support groups are full, and he receives thousands of requests for assistance every day, but he can only charge a cost equivalent to the materials used. This is not because he doesn’t want to help, but because the field of low-frequency noise detection and compensation is not well-established. Identifying the source of low-frequency noise requires extensive experience and specialized knowledge, which is currently lacking. Most companies claiming to solve the problem actually sell ineffective products (such as “sound-absorbing cotton”). Even if Zhu Lin worked around the clock, he could only handle a few hundred cases per year, which is far from meeting the needs of millions of victims nationwide. This field, which intersects acoustic and structural engineering, was previously neglected and is now being filled by individual enthusiasts like him.
The old problems remain unaddressed, and new threats loom with the AI era
While people are still dealing with issues like old building components (pumps, air conditioning units), new, more significant sources of low-frequency noise are emerging. With the rapid development of AI, large data centers are being built across the country, generating significant amounts of low-frequency noise. In places like Michigan and Wisconsin in the U.S., residents are already suing companies like Microsoft and xAI. Many locals prefer to live near nuclear power plants rather than data centers. In China, there are no specific standards for low-frequency noise, and the new building regulations have only reduced the standard for floor impacts to 65 decibels, which only addresses part of the problem. If no mandatory standards for low-frequency noise absorption are established for new data centers and commercial buildings, another wave of low-frequency noise will soon hit people.