We constantly detect the sound that surrounds us. Even in conditions that we may consider to be total silence, there is still background noise; it just cannot be detected by the human ear. Sound is actually variations of pressure. It travels in the form of sound waves via mediums of solids, fluids, or air. We hear through amplifying and detecting those vibrations, and they are converted into electrical signals that get interpreted inside our auditory cortex.
Hearing is measured in decibels and is one of the five senses that is a very important part of our daily lives. It can bring us joy and helps to keep us safe. However, if we become overloaded with sensory input in terms of unwanted noise pollution – it can lead to our senses being overloaded and result in poor health and stress. That is why it is critically important to control noise levels inside the buildings that we work and live in.
What is Structure Borne Sound?
The transmission medium is what turns a sound into being ‘structure borne’. These sounds, in contrast to vibrations that travel throughout the air, travel through solids like steel, concrete, and wood. In basic terms, this applies to noise that is generated inside of a building. Examples of structure borne noises or sounds are a slamming door, restaurant acoustics or heavy footsteps coming from a neighbour upstairs. Heavy footsteps can cause vibrations inside the floor’s structure, which are directed upwards as well as downwards through the ceiling.
Five Structure Borne Processes
The generation of structure borne sound, as well as its transmission, is divided into five separate processes:
1. Generation – the oscillation source.
2. Transmission – oscillatory energy being transferred from the source to the building structure.
3. Propagation – the mechanism that distributes energy through an entire structure.
4. Attenuation – as sound waves move throughout the structure, they are reflected partially off of surfaces, which diminishes the sound and reduces their energy.
5. Radiation – sound being emitted out of an exposed surface. This creates airborne sound in addition to structure borne sound.
Why is Structure Borne Sound So Important?
Given that the leading cause of disputes between neighbours is noise complaints, along with the negative impact that unwanted noise can have on wellbeing, it is very important to carefully consider the risk of structure born sound whenever buildings are designed and renovated. The Building Regulations Approved Document E from the Government on resistance to sound set out minimum standards for the impact of sound insulation between and within buildings – which includes schools as well as offices and homes. The strict criteria that are set forth in the document have been designed to mitigate noise production within the actual structure.
How is Structure Borne Sound Measured?
The transmission of impact sound is measured in sit through the use of a tapping machine that has steel-faced hammers for striking the test surface. This sound is measured and recorded in decibels, in an adjacent area. However, it does not consider the various noises that may be produced. Therefore numerous measures are instituted to help reduce structure borne noise.
Methods for Reducing Structure Borne Sound
In order to reduce structure born sound, the key is to dampen or weaken the vibrations that are causing the source of the sound. The following are methods that are used to mitigate structure borne sound being produced:
- Padding and carpet – laminate or wooden floors might be attractive, but they create high amounts of structure borne sound. So wherever possible, it is best to use carpets.
- Resilient underlay – normally made from recycled foam or rubber or rigid fiberglass the materials work in a way that is similar to padding and carpets.
- Soundproofing compounds – often installed in between two rigid structures like subflooring. While they are moving through a structure, they dissipate the vibrations.
- Make a gap – the best way that structure born sound can be reduced is to have a solid structure, followed by an air gap, and then another solid structure. Contact between masses can be broken up by installing secondary wall structures, raised floors, or suspending ceilings. The methods can all help to break up contact as well as reduce sound wave transmission. High mass constructions also incorporate cavities or offset construction is deployed to help prevent this type of transmission from occurring.
- Install anti-vibration solutions – spring ceiling hangers, sound clips, and anti-vibration mounts, all can help to dampen structural borne sound.