Introduction
Sound can have a significant impact on our physical and mental wellbeing. It can produce both positive and negative effects. This has been corroborated by several sound focused studies. One example of the positive being the 2021 Frontiers in Psychology review by Eleanor Ratcliffe, titled Sound and Soundscape in Restorative Natural Environments. It highlights how natural sounds like birdsong, flowing water, and wind can help reduce stress, improve mood, and cognitive performance.
However, not all sounds are helpful. When unwanted or excessive, they become noise. Interest grew notably after the World Health Organisation identified noise as a global public health issue in their 2018 Environmental noise guidelines for the European Region. They outlined how environmental noise can lead to serious health problems like sleep disturbance, heart disease, and cognitive impairment in children. In England, a study conducted by the UK Health Security Agency (UKHSA) in 2023, found that 40% of adults were exposed to harmful road noise, with a smaller but significant exposure to rail (4.5%) and aircraft noise (4.8%). Annually, these exposures amounted to the loss of approximately 127,000 years of healthy life due to illness and early death.
Numerous surveys have also brought to light the issue of noise intrusion in UK homes. The Chartered Institute of Environmental Health Survey conducted between 2019-2020 and 2020-2021, found a 54% rise in noise complaints in 89 local authorities that provided data for both years. Additionally, the English Housing Survey 2023 to 2024: drivers and impacts of housing quality found that around 6% of all homes in England reported problems with external or neighbour noise.
These findings underscore the importance of considering sound when designing buildings and spaces. This post will help you understand sound and noise so that you are equipped to design acoustically comfortable buildings that support user wellbeing. Read on for some useful insights.
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What is Sound?
Sound is a form of energy that travels through mediums like solids, liquids, or gases and is produced by vibrating objects. The object, perhaps a speaker, can be referred to as the source of the sound. As the source vibrates, it causes nearby particles in the medium, let’s say air particles in air, to vibrate as well. These vibrations pass from particle to particle, creating a wave that moves outward. When sound waves reach our ears, they create vibrations on the eardrum that are turned into electrical signals the brain understands as sound.
There are two ways to describe sound: amplitude and frequency.
Amplitude
Amplitude refers to the strength of a sound wave. Our brain interprets this as loudness. Low amplitudes produce quiet sounds (like a whisper), while high amplitudes produce loud sounds (like traffic noise). In air, amplitude is expressed as Sound Pressure Level (SPL), and its unit is the decibel (dB).
Humans can typically hear sounds starting from around 0 dB, which is dubbed the threshold of hearing, up to 120-140 dB which is known as the threshold of pain. Sounds above this level can cause immediate hearing damage.
The following are examples of sound pressure levels reached in different environments:
Frequency
Frequency, on the other hand, refers to how often a sound wave vibrates per second. Our brains perceive this as pitch. Low frequencies produce deep sounds (like thunder), while high frequencies produce high-pitched sounds (like a whistle). Frequency is measured in Hertz (Hz).
The range human beings can hear lies between 20 Hz and 20,000 Hz (20 kHz). However, this range can shorten with age or prolonged exposure to loud sounds.
What is Noise?
Noise encompasses all unwanted and unpleasant sounds. Sounds become harmful when they become excessive or poorly managed. Noise is perceived as a nuisance and can cause a plethora of negative physical and mental health issues.
As mentioned earlier, noise can have many different impacts on people’s lives, including:
- Hearing loss
- Reduced quality of life
- Interference
- Distraction
- Expenses
- Increased stress and sensitivity
There are two broad categories of noise:
Environmental
This refers to unwanted sound from external sources that affect people in homes, schools, hospitals, and public spaces. It includes traffic noise, both continuous (like a busy road) and intermittent (like passing aircraft or trains). Noise from leisure and entertaining also falls in this category.
Environmental noise can interfere with concentration, work performance, rest, and sleep. Even when inside buildings, we may still experience this noise through poorly insulated walls, windows, or services.
Occupational
This relates to noise in the workplace. This includes sound form machinery, tools, construction sites, industrial processes. It also applies to high-noise work environments like nightclubs, music venues, or manufacturing plants, where exposure to sound is part of the job.
In indoor workplaces, noise may also come from building systems, equipment, or activity in adjacent spaces which can impact productivity and worker health.
The Labour Force Survey (LFS) presented that work-related hearing problems reached an estimated number of 12,000 workers from 2021-2022 to 2023-2024. The Health and Safety Executive (HSE) provides advice for managing noise and even has resources like their industry good practice guides that you can refer to: Noise at work
Noise Transfer in Buildings
There are three main action areas when considering noise in a building:
- Source – This may be from outside a building such as traffic noise, or within the building such as occupant noise.
- Path – The sound path may be from outside of the building or within the building.
- Receiver – The receiver of the sound may be the complete building, a room of the building or it could be the person that is hearing the sound.
Noise can be transferred to a building or between rooms in different ways, depending on the type of sound. There are two main types of noise transfer:
Airborne Noise Transfer
Airborne noise moves through the air until it hits a surface or barrier. This could be described as voices, radio, music, traffic noise and so on. These sounds travel through the air before reaching the building assembly, or partition.
Impact Noise Transfer
Impact noise is generated on a partition or building assembly. This could be described as footsteps, windows, or doors slamming, vibrating machinery and so on. This type of sound will usually travel through the air to reach your ear, but its source tends to be on the structure itself.
Even when a separating wall or floor is well insulated, noise can still travel in other ways. It may pass directly through the separating element, or indirectly via flanking paths, like continuous floor slabs or wall junctions.
Controlling Sound in Buildings
Sound inside buildings can pass through materials, reflect off surfaces, or travel as vibrations through structures. To manage these behaviours, four main strategies can be used:
Insulation
Reducing the amount of sound energy that is transmitted to an adjoining airspace. It is used to control airborne and impact noise travelling between rooms or from outside.
Absorption
Reducing the sound energy reflected by the surfaces within a room. Generally speaking, sound absorption has an effect on the quality of sound, rather than reducing the noise itself.
Diffusion
Scattering reflected sound in multiple directions to create a more even sounding internal environment. It is useful for large or open spaces.
Isolation
Reducing structure-borne noise by preventing vibrations from spreading through the building. It is often used around machinery and at junctions between building elements to break the path of vibration.
Each method addresses a different aspect of sound behaviour, and good acoustic design will often employ them in combination.
Common sound insulation products include:
- Absorption materials – acoustic panels
- Glazing types – double glazing
- Vibration isolation components – acoustic underlays
- Insulation materials – mineral wool
- Sealing and barrier systems – acoustic sealant
Designing for Sound Insulation
Insulation helps to control the transmission of both airborne and impact noise. It is measured using the sound reduction index (R), which is the measure of the insulation against the direct transmission of airborne sound. The index is measured at different frequency bands as insulation varies with frequency.
The following table looks at some common construction materials with their sound reduction indices measured at different frequencies. The higher the sound reduction (R) value, the better the material at reducing the transmission of sound.
Ensuring good sound insulation
When designing for sound insulation it is important to ensure airtightness and uniformity in the insulation. Air gaps will have an impact on overall performance. An example of this, if a brick wall contains a crack or hole that represents only 0.1% of the total area of the wall, the average SRI of the wall is reduced from 50dB to 30dB (McMullan).
Air gaps can be a particular problem around windows and doors, seals around partitions, joins with floors, ceilings, service pipes and so on.
It is also good to consider isolation, or discontinuous construction, which will help with the reduction of sound transmission. A good example of this would be the cavity in a window, floating floors, and resilient mountings used for vibrating equipment.
It is important to factor in existing sounds affecting a site early on in the design process. This is crucial in sites in close proximity to an airport or a busy transport hub for instance. The analysis should then inform major decisions.
One way to think of your acoustic design strategy would be to map out the activities that will be taking place within your building and rating them on a scale of which would produce the greatest amount of sound. This may help you visualise the problem at hand and prioritise the spaces that will need a more robust acoustic treatment.
You can also then use this to adjust your adjacency diagram and figure out which spaces are closest to which ones and what types of noise they are exposed to. For example, in a house, quieter spaces like bedrooms should be placed away from louder communal areas like kitchens and living rooms. It is also important to consider occupancy levels and how the noise will vary across the day.
Another factor to consider when designing ventilation strategies is the opening of windows in warm temperatures and whether this activity will be impacted by external noise levels. Reports indicate that occupants are more willing to accept higher levels of noise from outside for the sake of natural ventilation through windows on a warm day.
Working with Sound Insulation Regulations
Regulations for sound insulation tend to be most important in walls and floors shared between dwellings, for example flats or joined houses. There are also specific requirements for buildings such as hotels, student housing, schools, nursing accommodation where sound insulation between rooms and corridors needs to be considered carefully.
Generally speaking, the areas where sound insulation must be considered in order to comply with regulations are:
- The building envelope – all elements that separate the dwelling from external noises such as road, traffic, trains, and industry.
- Separating walls – all walls that are between dwellings and within the same dwelling.
- Separating floors – all floors between dwellings.
The Building Regulations Document Part E – Resistance to sound, require a minimum level of sound insulation for the building envelope and internal walls and floors, protecting from either airborne sound or impact sound, or both. The following diagram demonstrates the different requirements for a simple set of flats.
Walls tend to require insulation against airborne sound, while floors tend to require insulation from both airborne and impact sound.
The following tables adapted from the Building Regulations demonstrate the sound insulation standards required for separating walls and floors in houses and flats.
The following details are examples of guidance provided in the Building Regulations Document Part E – Resistance to sound, demonstrating examples of what is considered to be acceptable construction standards for sound insulation.
Robust Details
A great resource that provides detailed information and diagrams for many types of construction is the Robust Details Handbook. The book contains separating wall and floor construction details that comply with Part E of the building regulations ‘resistance to the passage of sound.’ The use of the scheme provides an alternative to pre completion testing for demonstrating compliance. The handbook can be downloaded from the Robust Details website.
The details cover timber frame, masonry, and steel frame construction – some examples follow:
Helpful Links
Human Perception of Environmental Sounds (Frontiers Research Topic)
Environmental noise guidelines for the European Region (WHO)
Environmental Noise and Effects on Sleep: An Update to the WHO Systematic Review and Meta-Analysis (PMC)
Spatial assessment of the attributable burden of disease due to transportation noise in England (ScienceDirect)
Noise and mental health: evidence, mechanisms, and consequences (Journal of Exposure Science & Environmental Epidemiology)
Noise survey (CIEH)
English Housing Survey 2023 to 2024: drivers and impacts of housing quality (GOV.UK)
Noise at work (HSE)
Noise induced hearing loss in Great Britain (HSE)
The Noise at Work Regulations 1989
The Control of Noise at Work Regulations 2005
Attenuated natural ventilation options
UK Building Regulations
Robust Details
Noise and Air Quality Viewer
Extrium
Books
Here are some recommendations for further reading:
Neufert – Architects Data
Modern Construction Handbook – Andrew Watts
Environmental Science in Building – Randall McMullan
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Conclusion
Sound is a vital part of how we experience buildings and poor acoustic design can have serious effects on health and comfort. By understanding how sound works and applying the right strategies during design, we can create spaces that are better suited to the needs of their users.
We hope you found this post insightful.
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Author
Written by Valanne Fernandes, a Part 2 Architecture graduate. Valanne is a content creator with First In Architecture, spending her time researching, writing and designing inspiring new content for the website.
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