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1. Acoustic environment of residential buildings
Residential buildings are important places for people to live, rest, and sleep. The quality of their acoustic environment not only affects the comfort of living, but also concerns the physical and mental health of the residents.
First, quiet is essential for home life, especially for rest and sleep. This requires buildings to minimize indoor and outdoor noise pollution, such as traffic noise from main urban roads, highways, light rail lines, and airports outside the window. Noise within the building should not be ignored either, including the rumbling of elevators, the hum of basement water pumps, the rotation of air conditioner outdoor units, the vibration of indoor heating units, the whirring of ventilation fans, the buzzing of transformers, the flushing sound of PVC drain pipes, the roar of generators, the drainage sound of underground sewage pumps, the turbulent sound of water pipes running from faucets, and the slamming sound of doors closing. These noises greatly disturb and damage people's peaceful living environment.
People live in their own spaces and need privacy from each other. For example, two neighboring families should neither see nor hear each other; otherwise, it would not only be awkward but also prone to conflict. Sound insulation in buildings is the fundamental guarantee of privacy. Due to different transmission mechanisms, sound insulation is divided into two main categories: one is airborne sound insulation. Airborne sound refers to the process where sound is emitted from a source, first travels through the air, then impacts building structural components causing vibration, and finally radiates sound into another space. Examples include talking and television sound. The other category is impact sound insulation. Impact sound refers to the process where a sound source directly impacts structural components, causing vibration, and then the vibration radiates sound into another space. Examples include footsteps upstairs, children running and jumping, and the sound of furniture being dragged.
As people's living standards continue to improve, residents' demands for a better acoustic environment are also increasing, making sound insulation and noise reduction a growing pain point in residential quality. However, in the past, due to economic considerations during construction, acoustic environment standards were relatively low, lagging far behind those of developed countries. For example, the nighttime noise limit for residential buildings was only no more than 37 dBA (the WHO recommended 30 dBA in 2000), the airborne sound insulation limit for partition walls was only no less than 45 dB, and the floor impact sound insulation limit was no more than 75 dB. Furthermore, developers and design units had limited understanding of sound insulation and noise reduction, resulting in a long-standing low quality of residential acoustic environment in my country. Even with low standards, non-compliance still occurs frequently, and complaints about noise pollution and sound insulation problems are commonplace.
Since 2020, the national and local governments have introduced higher noise and sound insulation standards for densely populated residential buildings. For example, the Beijing local standard DB11/1740-2020 "Residential Design Code", which came into effect on January 1, 2021, first raised the limit of airborne sound insulation standard for partition walls from 45dB to 50dB and tightened the floor impact sound standard from 75dB to 65dB. This means that the sound insulation standards of newly built residential buildings in Beijing approved after 2021 must be significantly improved, otherwise they will be considered non-compliant. The national standard GB 55016-2021, "General Code for Building Environment" (all articles are mandatory, meaning all articles must be strictly enforced), which came into effect on April 1, 2022, raised the permissible nighttime noise limit for bedrooms from the previously uniform 37 dBA to 30 dBA for Class I acoustic functional areas, 35 dBA for Class II, III, and IV acoustic functional areas, and 33 dBA for sound sources within buildings. Furthermore, the newly revised and soon-to-be-promulgated "Code for Sound Insulation Design of Civil Buildings" GB... Standards 50118-2021 and the forthcoming new standard GB55xxx-2022, "Code for Design of Residential Buildings," have raised the sound insulation limit for partition walls from 45dB to 50dB, tightened the floor impact sound insulation limit from no more than 75dB to 65dB, and increased the sound insulation limit for street-facing windows from 30dB to 35dB. Furthermore, low-frequency noise limits have been added to the indoor noise standards, bringing my country's building sound insulation and noise reduction standards in line with those of developed countries. These standards will significantly improve the design standards for the acoustic environment of residential buildings, while also requiring design firms and developers to enhance their sound insulation and noise reduction design capabilities and increase their investment in these areas.
Previously, due to the lack of a closed-loop legal system, that is, the lack of laws and regulations to protect the entire construction process, including planning, design, construction, and sales, such as prior disclosure, in-process supervision, and post-event penalties, it was difficult to clarify and hold relevant responsibilities accountable even if the design or construction effect did not meet the standards. In addition, the noise insulation problem in residential buildings is often hidden. Developers and architects do not have it clearly visible on the architectural drawings as they do in the renderings. It is difficult for homebuyers to intuitively perceive it before moving in. Once problems are discovered after moving in, it is often extremely difficult to make up for them due to structural, decoration, load, and cost factors. As a result, the resulting conflicts often drag on for a long time, causing homebuyers great distress.
2. New requirements of the new noise law
The Law of the People's Republic of China on the Prevention and Control of Noise Pollution was adopted at the 32nd meeting of the Standing Committee of the 13th National People's Congress on December 24, 2021, and came into effect on June 5, 2022. It is referred to as the 2022 New Noise Law.
The 2022 Noise Reduction Law classifies residential buildings (mainly housing) as noise-sensitive buildings requiring quiet environments (see Article 88). It also imposes highly operable, closed-loop management requirements on developers, based on sound insulation and noise reduction standards, and with clearly defined legal responsibilities. This will have a profound and immediate impact on the acoustic environment protection of residential buildings after the law's implementation. Table 1 shows the specific provisions for developers under the new Noise Reduction Law. Table 2 lists the relevant articles on sound insulation and noise reduction for residential buildings under the new Noise Reduction Law.
4. Legal Liability
The biggest difference between the new Noise Level Control Law and previous laws is the clear definition of liability for violations by residential developers and sales companies. If developers or sales companies fail to disclose noise levels at the sales location, fail to include them in the sales contract, or fail to specify the location of shared facilities or the building's sound insulation in the contract, they are committing a violation. They may face penalties from housing authorities, and due to the prior violation, the sales contract can be declared invalid if the buyer requests it. If the disclosed information or sales contract contains falsification, or if noise levels or sound insulation figures are inconsistent with reality, the sales contract may be deemed invalid at best, and at worst, if it causes losses to the buyer, it may be considered fraud and subject to heavier penalties.
It should be noted that civil lawsuits concerning noise or sound insulation issues have been common in past judicial practice, even occurring frequently. However, previous national standards were relatively lenient. Most developers, under general building construction conditions, could generally meet or approach the limits (for example, the airborne sound insulation of commonly used aerated concrete blocks and panels was around 45dB under the old standard; the impact sound insulation of conventional floor slabs with insulation layers (such as 100-120mm thick slabs) was around 75dB under the old standard; and double-glazed windows that met insulation requirements could generally reduce outdoor noise to around 37dBA under the old standard). Therefore, even if homebuyers sued, their claims for refunds, repairs, and compensation were often difficult to obtain. In addition, previous noise environment lawsuits often involved many ambiguous legal boundaries and required highly specialized expert evaluation and evidence collection, resulting in lengthy litigation processes that left homebuyers exhausted and disheartened.
The new noise laws and standards are putting unprecedented legal pressure on developers and sales companies, forcing them to take residential sound insulation and noise reduction seriously. If they continue with their previous approach to acoustic measures, failure to meet standards is highly probable.
Article 1203 of Chapter Four, Product Liability, of the Civil Code stipulates that "If a defective product causes harm to another person, the injured party may claim compensation from the product's manufacturer or seller. If the product defect is caused by the manufacturer, the seller, after paying compensation, has the right to seek recourse from the manufacturer. If the product defect is caused by the seller's fault, the manufacturer, after paying compensation, has the right to seek recourse from the seller." Article 1207 stipulates that "If a person knowingly produces or sells a defective product, or fails to take effective remedial measures in accordance with the preceding article, causing death or serious harm to another person's health, the injured party has the right to claim corresponding punitive damages."
Noise and sound insulation issues can harm homebuyers' health, lead to neighborhood disputes, and potentially cause damage. According to the aforementioned legal provisions, if the acoustic quality of a residential property fails to meet standards, homebuyers can seek compensation according to law.
In particular, with stricter acoustic standards in the future, if developers or sales companies fail to prioritize and invest adequately beforehand, resulting in non-compliance with standards, and homebuyers pursue legal action based on health hazards, neighborhood disputes, or other reasons, this falls under the category of "environmental pollution disputes." In this case, the developer or sales company must "reverse the burden of proof," meaning they must provide legal evidence to prove that the problem was not caused by the residences they sold. This puts the developer in a very passive position. The legal basis for this is Article 1230 of Chapter VII of the Civil Code, concerning liability for environmental pollution and ecological damage, which stipulates that "in disputes arising from environmental pollution or ecological damage, the party responsible shall bear the burden of proof regarding the circumstances under which they are not liable or have their liability mitigated as stipulated by law, and the absence of a causal relationship between their actions and the damage."
Another crucial issue is the collection and evaluation of evidence. According to Chinese law, civil cases should adhere to the principle of "transparent evidence collection," meaning that both parties must agree on the methods used for evidence collection. In the case of residential acoustic environments, this means both parties must agree on a qualified appraiser, and both must be present during the testing. The legal basis for this is Article 67 of the Civil Procedure Law of the People's Republic of China: "The parties have the responsibility to provide evidence for their claims." Article 79 states: "The parties may apply to the People's Court for expert evaluation on specialized issues concerning the ascertainment of facts."
When a party applies for an expert evaluation, the qualified expert shall be determined through consultation between the two parties; if no agreement can be reached, the People's Court shall appoint an expert. Previously, homebuyers were eager to resolve issues and actively promoted the evidence collection process, while developers or sales companies (property management companies) were often in a passive cooperating role, frequently resorting to shirking responsibility, delays, or even interference with evidence collection. However, with the implementation of the new Noise Law, which features higher standards, greater difficulty in meeting requirements, clearer legal responsibilities, and the "reversal of the burden of proof," the situation may reverse. Developers or property management companies will be more anxious, because if the "reversal of the burden of proof" exceeds the statute of limitations, they will often be found guilty.
3 Technical Issues
Laws and regulations set forth institutional requirements, while standards and specifications provide upper limits for indicators. So, specifically, what sound insulation and noise reduction issues in residential buildings require serious attention?
Project site selection is crucial for the quality of the regional acoustic environment. To avoid noise pollution, residential sites should ideally be located away from areas with poor noise environments, such as airports, train stations, light rail lines, highways, and industrial zones. Traffic noise is very common for residences near streets, especially when near highways, railway lines, or urban rail transit, where the noise impact is even more significant. To reduce noise pollution, measures such as sound barriers and green belts can be used. Furthermore, topographical conditions (such as slopes and high embankments) and the mutual shielding relationships between buildings can be utilized effectively. When traffic noise cannot be avoided for various reasons, soundproof windows can be used to protect the indoor acoustic environment of residents. However, this method is very passive because it restricts ventilation.
The planning within a residential area can significantly impact the acoustic environment. Reasonable layout and the use of shared buffer zones should be employed to reduce the impact of vehicle noise; noise sources such as machine rooms and boiler rooms should be centrally located and subject to centralized noise reduction measures; and noise from social activities within the residential area (such as ground-floor shops) should be reasonably controlled and isolated. Planning methods should be effectively used to create a good acoustic environment within the residential area.
Noise pollution caused by poor residential floor plan design is often regrettable. Noise-sensitive rooms such as bedrooms and living rooms should ideally avoid facing the street. If this is unavoidable, enclosed balconies can be installed to create a buffer soundproof space. Large panoramic windows, floor-to-ceiling windows, and bay windows with large sound transmission areas should be avoided as much as possible. When designing the floor plan of a residential unit, rooms with similar functions should be arranged on both sides of the partition wall. Bedrooms, living rooms, and studies should be effectively separated from noise-insensitive rooms such as kitchens, bathrooms, and dining rooms. Elevator shafts should not be adjacent to bedrooms or living rooms. This is because the vibration of the elevator during operation is transmitted through the tracks in the shaft to the partition walls, directly radiating noise into the residents' homes. In China, disputes caused by elevator noise pollution are countless, and the root cause is almost always the close proximity of rooms on the floor plan. If the design includes a bedroom or living room adjacent to an elevator, the elevator shaft must be effectively treated for sound absorption and insulation, and the top-floor machine room also needs vibration isolation treatment for the traction machine.
It is necessary to prevent noise interference from equipment and facilities such as machine rooms, water pumps, fans, and transformers within the residential area. These facilities should not be located adjacent to bedrooms or living rooms. Often, due to factors such as floor area ratio, noisy equipment like water pumps and transformers are located on the basement level. When these devices are running, residents on upper floors will be affected by secondary noise generated by structure-borne sound, and this structural noise may extend beyond the first floor. To prevent this, it is essential to employ a comprehensive and effective approach, including sound absorption, sound insulation, and vibration reduction, based on the vibration characteristics of the equipment. In particular, addressing vibration isolation (e.g., using floating foundations, replacing with high-efficiency vibration dampers, and using flexible connections) is crucial to effectively reduce the noise interference from equipment and facilities.
There is a growing trend of indoor equipment, such as sanitary ware, water supply and drainage pipes, exhaust systems, and air conditioning fan coil units in high-end residences, whose noise pollution cannot be ignored. It is important to select low-noise equipment (such as cast iron drain pipes, silent water pipes, silent fans, and silent fan coil units) or low-noise systems (such as same-floor drainage technology and 100% fresh air conditioning systems) to reduce indoor noise. Noise parameters should be considered as an important evaluation indicator when selecting indoor equipment to prevent disruption of the quietness of the residence.
4. Cost Issues
Any performance improvement inevitably comes at a cost. Under the strong impetus of the new noise law, developers may need to hire architects or acoustic consultants with more experience in sound insulation and noise reduction to address acoustic technical issues in pre-contractual legal documents such as "publicizing noise levels and prevention measures" and "incorporating them into the sales contract." They may need to commission professional acoustic testing units to test and even verify the sound insulation and noise reduction effects. They may need to purchase walls, floors, and even doors, windows, and equipment with better acoustic performance (especially to improve sound insulation, it may be necessary to use thicker walls or floors, resulting in a reduction in usable floor area or ceiling height). Furthermore, they may even face legal penalties for failing to meet noise insulation standards due to insufficient experience. All of these factors can contribute to costs!
In fact, sound insulation and noise reduction is a chain-like system engineering project that includes planning, design, construction, materials, acceptance, and delivery. The more thorough the pre-treatment measures are, the lower the cost may be in subsequent stages.
For example, during the site selection and planning phase, fully utilizing computer simulation technology to optimize the design of residential noise reduction distances or the obstruction relationship between buildings achieves better noise reduction results, which is more efficient and cost-effective than the passive method of purchasing soundproof windows after the fact. Furthermore, fully utilizing load-bearing walls as partition walls in architectural design (heavy walls naturally have higher sound insulation, i.e., the mass law in sound insulation theory) is more space-saving, labor-saving, material-saving, and cost-effective than being forced to use thick, high-sound-insulating lightweight walls. In the construction and material selection stages, adding mid-term acoustic testing on-site and laboratory verification testing of materials is much more proactive than the "locking the stable door after the horse has bolted" approach of discovering poor sound insulation in concealed construction or that substandard acoustic materials have already been installed after completion. Finally, leaks and gaps during construction must be effectively sealed; otherwise, even with high sound insulation in walls or floors, sound leakage through gaps will significantly reduce sound insulation performance.
In addition, some sound insulation and noise reduction measures may incur hidden additional costs. For example, floating floor structures that reduce the impact sound of floor slabs require a thicker concrete layer on the vibration damping pad to achieve higher sound insulation performance, which directly increases construction costs. Moreover, a thicker concrete pad means a greater weight load, which requires larger and thicker beams, columns, and foundation structures, thus creating hidden additional costs.
In conclusion, the cost of sound insulation and noise reduction in residential buildings can be greatly optimized through scientific and reasonable acoustic control at each stage; otherwise, it will inevitably be a case of getting twice the result with half the effort.
5 Conclusion
As the renowned architect Louis Kahn once said, quiet and light together compose the "soul of the environment." Quietness brings comfort and health, helping people concentrate, while noise and clamor disturb and annoy. Throughout millions of years of human evolution, the natural environment has been largely quiet, and our genes also seek tranquility. Only in the last 100 years, with the advent of industrialization, has noise gradually spread, continuously polluting our surroundings.
Sound is an inseparable part of life, and the acoustic environment of residential buildings is something we experience daily, much like our daily meals. We don't need the annoying noise of fried or puffed foods; what we need is a quiet environment that is nourishing and of high quality. The new noise law sets higher standards for sound insulation and noise reduction in residential buildings. Developers and designers must adopt practical and feasible technical measures to reduce noise and improve sound insulation, meeting or exceeding national and local limits, in order to provide a fundamental guarantee of health for the most basic and precious human needs, such as quiet sleep and rest.
Source: Tsinghua University Acoustics Laboratory
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