Sound reduction , Architectural

Sound insulation prevents two kinds of sound transmission: airborne sound and impact sound.

The conventional rule for reducing sound transmission is the mass law. This says that the heavier the structure, the less sound it will transmit. However, other factors, such as discontinuous construction and stiffness, mean it is possible to achieve good sound insulation levels with lightweight construction, making the most of the drywall advantage.

One of the most important features of sound insulating structures is that they should be imperforate. Even the smallest of cracks, say only 0.4mm wide, has a significant area along the length of a wall, and could halve the effectiveness of a 50dB partition.

Sound frequency
Structures have variable sound insulation values depending on the frequency of the sound. With Lafarge’s twin frame partitions significant improvements can be made, especially in insulating against higher frequencies.

Effects of sound reduction values on audibility
Rw Conversation level
30 dB Normal conversation can be distinguished
35 dB Loud conversation can be distinguished
40 dB Loud conversation can be heard but not clearly distinguished
45 dB Loud conversation can just be heard but not distinguished
50 dB Shouting can just be heard but not distinguished

Acoustics
In domestic buildings, acoustic factors are not very critical. Most of the necessary sound absorption will be provided by the furnishings and occupants. However, with auditoria of all types the design problems are complex, and acoustic specialists should be consulted. Despite the complexity of acoustic science, some basic principles are universal:
• Provide direct sound paths between sound sources and listeners – consider raking floors and try to avoid columns.
• Beware of curved surfaces – convex shapes scatter sound and concave shapes focus it, often with disastrous results!
• Optimum reverberation times will depend on the use of the space and will be longer for music than for speech. With unwanted sounds, for example the noise of machinery, it is best to shorten the reverberation time as much as possible.

Acoustic tests determine partition performance

Partition Wizard

Typical Plasterboard Sound Reduction Performances