We detect sound all around us, at all times. Even in what we’d consider complete silence, there will still be a background noise, it’s just not detectable to the human ear. Sound is actually variations in pressure, and travels as sound waves through mediums of air, fluids or solids. The way that we hear is by detecting and amplifying these vibrations, and then converting them to electrical signals that are interpreted within the auditory cortex. Measured in decibels, the ability to hear is one of our five senses and is an essential part of everyday life. It keeps us safe, brings us joy but – if overloaded with sensory input in the form of unwanted noise pollution – our senses can hit overload leading to stress and ill health. It’s therefore incredibly important to control noise in the buildings we live and work in.
What is Structure Borne Sound?
What makes a sound ‘structure borne’ is essentially the transmission medium. As opposed to vibrations that travel through air, structure borne sounds travel through solids such as wood, concrete and steel; in its simplest terms, it applies to noise generated in buildings. Heavy footsteps from an upstairs neighbour or hearing the noise of a slamming door are all examples of structure borne sound, or structure borne noise. Those heavy footsteps have caused vibrations within the structure of the floor, which direct both upwards and downwards through your ceiling.
The Five Processes of Structure Borne Sound
The generation and transmission of structure borne sound is divided into five distinct processes:
1. Generation – the source of the oscillation.
2. Transmission – the transfer of the oscillatory energy to the building structure from the source.
3. Propagation – the mechanism by which the energy is distributed through the entire structure.
4. Attenuation – as the sound waves move through the structure they will be partially reflected off of surfaces, reducing their energy and diminishing the sound.
5. Radiation – the emission of sound from an exposed surface, which will create not only structure borne sound but also airborne sound.
Why is Structure Borne Sound Important?
Given that noise complaints are the number one cause of neighbourly disputes, and the detrimental impact unwanted noise can have on our everyday wellbeing, it’s important to give careful consideration to the risk of structure borne sound when designing and renovating buildings. Indeed, the Government’s Building Regulations Approved Document E ‘Resistance to the passage of sound’ sets out minimum standards for impact sound insulation both within and between buildings – not just homes and offices, but also within schools. The strict criteria set out within this document are designed to mitigate the production of noise within the structure itself.
Control of structure borne sound is also an important consideration in sensitive building structures, such as recording studios, where external noise needs to be kept to an absolute minimum.
How is Structure Borne Sound Measured?
Impact sound transmission is measured in situ, using a tapping machine with steel-faced hammers to strike the test surface. The sound is recorded and measured in decibels, in the adjacent space. However, this won’t take into consideration the variety of noises that could be produced, so a number of measures are deployed to reduce structure borne sound.
Methods to Reduce Structure Borne Sound
The key to reducing structure borne sound is weakening or damping the vibrations caused by the source of the noise. Here are the methods employed to mitigate the production of structure borne sound:
• Carpets and padding – those wooden or laminate floors may look amazing, but they’ll create a huge amount of structure borne noise, so it’s better to use carpets where possible.
• Resilient underlay – generally made from rigid fibreglass, recycled rubber or foam, these materials work in a similar way to carpets and padding.
• Soundproofing compounds – typically installed between two rigid structures, such as subflooring, soundproofing compounds dissipate the vibrations as they move through the structure.
• Create a gap – the best way to reduce structure borne sound is to have a solid structure, then an air gap, then a solid structure again. You can break up contact between masses by installing suspended ceilings, raised floors or secondary wall structures. These methods will all help break contact and reduce transmission of any sound waves. In the same way, high mass constructions will incorporate cavities or deploy offset construction in order to prevent such transmission.
• Install anti vibration solutions – anti-vibration mounts, sound clips and spring ceiling hangers can all dampen structural borne noise.
As well as installing anti-vibration dampeners, there are also a range of simple fixes for those struggling with structure borne – and resultant airborne – noise within an existing building. Firstly, check for cracks in the walls or any gaps around the windows or doors. Sealing these up could help reduce unwanted sounds. Be aware that installing double glazing tends to help more with insulation than actual sound proofing. Secondly, there’s a product known as ‘acoustic wallpaper’ that can reduce the associated airborne noise created by structural vibrations. Similarly, soundproofing curtains have also been shown to help block unwanted sound transmission.
Why you need an Acoustic Consultant?
The process of eliminating structure borne sound is complex, it will depend not only on the source of the noise but also the composition of the structures through which the vibrations pass, the radiating surface and design of the receiving spaces. While there are several building design features that can be incorporated to help mitigate noise pollution, many Architects and construction companies employ the services of a specialist Acoustic Consultant. An Acoustic Consultant will help assess, design, manage and control structural and airborne vibrations, minimising the risk of noise pollution and ensuring building standards are met.
At Auricl, our team of Acoustic Consultants can help you at every stage of the building process – from the assessment, planning and design, to the build itself. We provide practical, friendly, clear advice and pride ourselves on our bespoke service. We operate across London and the South East. If you’re looking for an Acoustic Consultant to help control structure borne sound, then for our London office contact us on 020 7859 4530 and for the Reading office dial 0118 207 7324. Or you can email us on hello@auricl.com. We look forward to providing the service you need.
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