The purpose of acoustic control is to limit noise pollution from external sources or from activities within the building. Noise can be described as unwanted sound, the intensity of sound depends on pressure levels which are measured in decibels (dB).
The human ear responds to sound intensity which also depends on the pitch. Pitch frequency is expressed in cycles per second, hertz (Hz).
The following are typical examples of sound pressure levels:
|Ear drum pain threshold||
|Aircraft taking off||100 dB|
|Pneumatic drill||90 dB|
|Vacuum cleaner||60 dB|
|Sound Proof Room||10 dB|
Most noises are made up of a number of individual sounds at various frequencies, all added together, so to get a better picture of the noise a graph is used to show the sound pressure level at various frequencies within the audible range.
The building envelope can play an effective part in controlling and absorbing sound energy by acting as a barrier to noise.
Sound Insulation in Buildings
Sound Insulation in Buildings Sound insulation refers to the ability of the building fabric to resist the transmission of airborne and impact sound.
Airborne sound insulation refers to sound insulation between:
- vertically or horizontally adjacent rooms where the sound source is airborne, for example, loudspeaker, speech or TV; or
- the inside and outside of a building
Impact sound insulation refers to sound insulation between vertically adjacent rooms where sound source is an impact, for example, footsteps.
Airborne and impact sound insulation are determined by both direct and flanking sound transmission. Direct transmission is sound transmitted directly through a wall or floor element, and flanking transmission is structure-borne sound travelling down a wall or floor into another room.
Room acoustics usually refers to the acoustic quality of rooms in terms of their reverberation time and speech intelligibility. This is particularly relevant for educational buildings, offices, theatres, performance spaces, etc.
- Reverberation time is a measure of how long it takes a sound to decay in seconds. It is determined by the amount of sound absorption in the room and room volume.
- Speech intelligibility is determined by the position of the speaker and listener, room geometry, background noise level and reverberation.
Noise Control Measures
There are ways which acoustic insulation can be used to control noise:
- Controlling Transmission Loss – Transmission loss is the reduction in the amount of sound energy passing through the building element or assemblyroof- wall-floor. This is expressed in decibels (dB). Noise can be either impact sound or airborne
- Controlling Sound Absorption – Typically hard surfaces have a characteristic of reflecting sound and amplifying noise reverberation.
- Internal lining and ceiling systems – Acoustic performance systems are available from specialist suppliers.
The sound absorption coefficient of materials varies with the sound frequency hertz (Hz).
Façade Sound Insulation
Roof and wall sound insulation concerns only the airborne sound insulation of the roof and walls of the building facade to:
prevent excessive transmission of external noise, for example, road traffic, rail traffic, aircraft, etc. from outside to inside
prevent excessive transmission of internal noise, for example, machinery noise within industrial premises, from inside to outside
Sound insulation criteria are dependant on country specific regulations and client specification requirements which may also include Planning Authority constraints.
The sound absorption coefficient of a material defines how much sound it can absorb across the frequency range. The more sound absorbed, the less is reflected back into the room to cause reverberation.
Total absorption will occur if the material has an absorption coefficient of 1. The results for all Kingspan insulated panels are shown below.
If improved acoustic performance is required, e.g. higher sound reduction values or reduced reverberation times, Kingspan insulated roof and wall systems can be constructed as indicated below.
Two solutions are provided, one for low humidity environments where there is low levels of air moisture and/or reasonable ventilation, and the second is for higher humidity applications such as swimming pools.
Low Humidity Application
These designs are for enhanced acoustic performance in a high humidity environment, e.g. swimming pools, leisure centres, and other high humidity processing environments.
The construction is designed to prevent condensation occurring within the acoustic layer.
The construction is designed so that the thermal insulation requirement is provided solely by the insulated panels, and the acoustic layer is only used for acoustic absorption and sound insulation. To eliminate condensation in the cavity it is necessary to provide ventilation with air from inside the building. This can easily be achieved by incorporating extractor fans within the acoustic profiled liner.
High Humidity Application