What is sound?
In the physical sense, sound consists of vibrations or waves in an elastic medium whose frequency is in the audible range. These vibrations can be in the air (airborne sound) or in solids, for example masonry (structure-borne sound). What is measured is the sound pressure level, i.e. the intensity of the sound, and not the noise itself, as noise cannot be directly measured. The unit of measurement for sound pressure is the decibel (dB). The frequency is the number of sound waves per second, expressed in hertz (Hz). One hertz equals one vibration per second. It is important to note that all noises are made up of sound waves that are defined by their wavelength (1/wl = frequency) and amplitude, the magnitude of the wave. Humans can hear frequencies from around 16 Hz (low tones) to about 16,000 Hz (high tones).
In the construction industry, frequencies from 100 Hz to 5,000 Hz are of interest. For noise measurement in buildings, a frequency weighting filter is used that establishes a connection between sound pressure level and perceived noise volume. Known as an A-filter, it corrects the sound pressure level in a certain frequency range and attenuates high and low frequencies.
By this means, the human perception of the sound pressure level can be converted to a sound level expressed in the unit of measure dB(A). Depending on the frequency, the human ear perceives tones of the same sound pressure as different volumes. In residential buildings and hotels, sounds are considered disturbing starting at a volume of >30 dB(A).
Disturbance factors in buildings: structure-borne and airborne sound
Noise in buildings is often caused by technical infrastructure such as water supply and sewage lines that are poorly or insufficiently insulated. Certain things need to be considered in a building's technical systems to keep the noise level as low as possible. Both structure-borne and airborne sound are relevant for plumbing systems.
Airborne sound is created when the sound propagates directly to the air in the installation space and thus impacts the wall before it. The human ear can detect this kind of sound.
In structure-borne sound, the sound propagates via fastening points such as pipe supports. Humans cannot hear structure-borne sound, but still register it physically and are disturbed by it. Radiation from walls and floors turns structure-borne sound into airborne sound.
Both types of sound can be caused by water, for example when it flows down vertical pipes (falling sounds), hits a bend (impact sounds) or just flows through pipes (flow sounds). Both types of sound can be effectively reduced through protective measures, such as sound-insulating pipe cladding.
Making noise level reduction visible
To express this reduction visibly, the A-sound level reduction in dB(A) is used as the definitive measure for noise reduction as perceived by the human ear. It refers only to the sound spectrum used for the measurement. The frequency-dependent insertion insulation level is another measure. This can be shown as a diagram representing the reduction of the installation sound level (airborne sound) by a pipe cladding that insulates the structure-borne sound, compared to the lack of such a cladding. The insertion insulation level is frequency-dependent. That means that different installation variations, for example pipes running under plaster, have enormous influence on the insertion loss. Evaluating the noise reduction of construction products requires data on both the insertion insulation level and the A-sound level reduction.
What legal requirements and standards apply to sewage and waste-water pipes?
The standards and directives concerning sound insulation are very important in Germany. Distinctions are made between DIN 4109, VDI 4100, DIN EN 14366 and DIN 1986-100/DIN EN 12056. For residential buildings to conform to the highest quality standards, all four standards should be met. The minimum requirements for the soundproofing of technical systems, plumbing fittings and devices are defined in DIN 4109, “Soundproofing in building construction.” Per the German Federal Environment Ministry, the purpose of the stipulations in DIN 4109 is to ensure that people in “spaces requiring protection” such as living and sleeping rooms, offices and patient rooms are protected against “unacceptable disturbance” due to sound propagation. Products that do not meet the minimum requirements of DIN 4109 are not approved for use on sewage pipes.
In addition, VDI 4100 is used as a guideline in Germany. The VDI (Association of German Engineers) distinguishes among three sound insulation levels for measurement behind a solid wall (SSt I-III) and two sound insulation levels for measurement directly at the pipe (SSt EB I-II). While in apartment buildings the sound insulation levels are classified in the range from <30 dB(A) (SSt I) to <24 dB(A) (SSt III), in semi-detached and terraced houses these values are between <30 dB(A) and <22 dB(A). In owner-occupied houses between <35 dB(A) and <30 db(A) (SSt EB I-II). DIN EN 14366 defines a procedure by which the airborne and structure-borne sound caused by sewage and rainwater installations can be measured under laboratory conditions. DIN 1986-100/DIN EN 12056 regulate the necessary building and lot draining or drainage systems in buildings.
Plan sound insulation early
Kaimann products can be used for two kinds of noise reduction measures: sound absorption and sound insulation. In sound absorption, the sound energy is reduced, typically by conversion into heat; in sound insulation, the propagation of airborne and structure-borne sound is prevented by a barrier.
Kaivenience makes a major contribution to the soundproofing of sewage, wastewater and rainwater pipelines and to compliance with technical requirements. Applied to synthetic or cast-iron pipes, Kaivenience prevents vibrations from being transmitted by structures and also attenuates airborne sound. At a water flow of 2 l/s in a light sewage system of plastic, Kaivenience achieves a level reduction of up to 15 dB(A) in the installation space and up to 18 dB(A) in the room behind the installation wall.
Kaiflex ST is used in refrigeration and air-conditioning systems to insulate pipes and air ducts in highly frequented public and commercial buildings such as airports, large office complexes, hotels, as well as in residential buildings, industrial plants and shipbuilding. In addition to preventing condensation and saving energy, Kaiflex ST also performs an acoustic function, absorbing sound and dampening duct wall vibration.