In a large building, sound is both reflected by the hard surfaces within a room and transmitted to other rooms by the building’s structural materials. Therefore, buffering sound generally requires absorbing reverberations within individual rooms and reducing or preventing sound propagation between rooms. Although it can be costly to reduce the noise level in a large building, gains in productivity and energy efficiency may offset part of this expense.
In most buildings, some rooms will routinely be noisier than others. By “zoning” parts of the building for different noise levels, you can focus your large-scale soundproofing efforts on the most significant sources of noise and use less costly mitigation methods elsewhere. Acoustical zoning can also help you to designate buffer areas between different types of work spaces. For example, using a storeroom as a buffer area between a copier room and an office will reduce the amount of sound that travels from the louder to the quieter work space. This method can also be used to site quiet work spaces away from sources of outside noise.
Covering ceilings with a sound-absorbing material is generally the most important step in reducing a room's noise level. Although fabric barriers will work for this purpose, acoustical tiles are usually preferable from a technical and aesthetic standpoint. For best results, look for a lightweight tile with a high noise-reduction coefficient, or NRC. Note, however, that these tiles will not necessarily prevent the transmission of sound from one floor to another. To prevent this type of sound propagation, you may need to install a second, sound-insulated ceiling slightly below the existing one.
Wall hangings such as banners and drapes absorb sound, preventing it from reflecting off the walls. In large, reverberant buildings such as school auditoriums, sports facilities and churches, hanging these materials can be a low-cost method of reducing noise levels. Alternatively, specialized sound-absorbing draperies and panels are available from a variety of manufacturers.
Bare floors – especially those made of concrete or tile – can produce and reflect a large amount of noise. Carpeting can greatly reduce the amount of reverberating sound, while also muffling impact noises such as footsteps.
Windows and Doors
To block exterior sounds, keep doors and windows closed. When windows must be opened, choose windows on a quiet side of the building if possible. Single-pane windows provide little resistance to sound. Double-paned, double-glazed windows generally offer superior noise control. Similarly, cheap hollow-core doors should be replaced with solid wood or metal doors. It’s also important to seal cracks and install weatherstripping around doors and windows; this will reduce sound transmission in addition to saving energy.
Soundproofing insulation can both reduce reverberation within a room and prevent sound from traveling to other parts of the building. It usually consists of foam or fiber padding that goes inside the wall. The type of material required depends on the amount and frequency of noise produced; blocking certain sounds may require more than one type of insulating material. In some cases, it may be necessary to build and insulate “floating” interior walls to achieve adequate noise reduction.