When it comes to sound insulation installation in any building, an important factor to consider is structure-borne sound. But just what is it and what can be done in order to mitigate its effects? If you are in the need of acoustic consultants London please see here.
The Definition of Structure-Borne Sound
First and foremost, sound can be defined as the pressure waves or oscillations resulting from a vibrating object or particle displacement. It’s crated by pulses that move through a certain medium to the human ear or detection device. In buildings, sound is categorised as structure-borne or airborne. The former, according to the British Regulations Approved Document E, can be defined as ‘sound that’s transferred through the structure of a building. A good example of structure-borne sound is the noise of footsteps on an upper floor that’s audible in the room below. Technically, this form of sound can be divided into the following different processes:
(i) Generation- this is the actual origin of the oscillation.
(ii) Transmission- this entails the transfer of the oscillation’s energy, from the origin through the building’s structure.
(iii) Propagation- this is the process that distributed the oscillation’s energy across the building’s structure.
(iv) Attenuation- this is the reflection of sound waves after bouncing off surfaces within the building, effectively diminishing their energy and ultimately the sound.
(v) Radiation- This entails the creation of vibrations from an exposed surface. Both the structure-borne and airborne sounds are naturally linked and so, the oscillations that rebound from a hard surface in a building are converted into airborne sound.
Similarly, airborne sound can cause some elements of the structure when it comes into contact with a non-insulated surface.
Ways to Minimize Structure-Borne Sound
There are several ways to mitigate the effects of structure-borne sound. These include:
-Installing padding and carpets with the aim of absorbing sound waves
-Installing sound clips, resilient mounts and spring ceiling hangers where appropriate.
-In some places, using resilient underlay made from recycled rubber, rigid fibreglass and foam can be an effective solution to reducing structure-borne sound.
-In places of the building like soundproofing and subflooring substances can be installed between two rigid structures. The compound works by dispersing the vibrations created by sound waves as they navigate through the structure.
-High mass structures that employ offset construction or cavities can be used in order to bar the passage of vibrations.
-You can also reduce structure-borne sound through raised floors, a secondary wall structure or a suspended ceiling system.
Even though structure-borne sound can be diminished by using the right structure design features, it’s actually a complex issue that calls for professionals. The nature of this form of sound depends on an array of factors including the radiating surface, nature & fabrication of the spaces as well as structural composition. As such, it is usually best to use a specialist acoustic consultant.
What is the Minimum Expected Impact Standard for Sound Insulation?
The Approved Document E, which we mentioned earlier defines the minimum acceptable noise insulation standard. The impact sound transmission has to be measured, often using a tapping device to hit a test surface, producing sound in an adjacent section. The impact of the structure-borne sound is then measured and carefully monitored.
As earlier mentioned, structure-borne sound consists of 5 processes:
Generation, which is the oscillation’s origin.
Transmission, which is the movement of oscillatory energy from the origin to the surroundings.
Propagation, which is the distribution of sound energy throughout the structure
Attenuation, which is the reflection of sound waves after coming into contact with a hard surface, thus the reduction of sound energy.
Radiation, which is the release of sound from a non-protected surface.
Both airborne and structural-borne sound are considered separate entities, but they are intrinsically connected. Airborne sound can cause a structure to vibrate when it comes across a surface. In turn, structural vibrations can radiate off surfaces, resulting in airborne sound.