(of exterior structures of buildings), the attenuation of sound as it penetrates the exterior of buildings; in the broader sense, the aggregate of measures taken to reduce the level of noise entering a room from the outside. The quantitative measurement of soundproofing, expressed in decibels (dB), is called the soundproofing coefficient.

A distinction is made between soundproofing against air-borne sounds and against sounds caused by impacts. Airborne soundproofing insulation is marked by reduction in the level of the sound (for example, speech, singing, or radio programs) when it passes through an enclosure; it is evaluated by the frequency response over the range from 100 to 3,200 hertz, taking into account the sound absorption of the premises being soundproofed. Soundproofing against impacts (people’s footsteps, moving furniture, and so on) is a function of the sound level produced under the floor and is evaluated by the frequency response of the normalized sound pressure level produced in the same frequency range when a standard impact machine is operating on the floor, also taking into account the sound absorption of the premises.

The inner walls and partitions of buildings should have a standard soundproofing coefficient for airborne sound; the floors between stories should have a standard coefficient for both airborne and impact sounds. To increase the soundproofing coefficient of the walls between apartments, as well as to reduce their weight, sectional structures with a continuous airspace or laminated structures made from separate layers of materials whose physical properties differ sharply are used instead of homogeneous structures, which consist of a single material or several rigidly joined layers of different materials (for example, a plastered brick wall).

The soundproofing of walls that have windows or doors is determined in practical terms by the sound insulation of the openings, which is usually less than that of the blank walls of the enclosure. The use of floors of the sectional type, with a continuous airspace, or with suspended ceilings, is expedient in improving their soundproofing qualities or in reducing their weight without affecting the level of soundproofing. Insulation of homogeneous floors against impact noise is improved by using floors with an elastic foundation or individual pads made of elastic materials. Flooring made of soft roll-type materials, which may have a thermally insulating or soundproofing base, is also recommended. The elastic pads under floors can be made of rock or glass wool or wood fiberboard.

The quality of the construction and assembly work is of great importance in providing the required soundproofing; even very minor cracks, holes, and fissures in structures will drastically reduce their soundproofing properties. In the planning of buildings, consideration should be given to the fact that the proper arrangement of a building, reduction of the noise from plumbing and engineering equipment, and rational design of the enclosures should also provide for insulation of edifices from internal and external noise. The greatest technological and economic effect is attained by the composite protection of buildings from noise.