The most important aspect of sound insulation in curtain wall facades is the partitioning against external noise. Depending on the external noise level, the façade is classified in a noise level area and the requirements for sound insulation are specified. The external noise level is made up of all types of urban noise. In addition, longitudinal sound transmission in the vertical and horizontal direction through wall and ceiling connections plays a role.
“DIN 4109 sound insulation in building construction” regulates the minimum requirements for protection against external noise. Measured and classified with the evaluated sound insulation dimensions R’w facades become “DIN 52210 Building Acoustic Tests”. “VDI Guideline 2719 Sound insulation of windows and their additional equipment” specifies sound insulation classes 1 to 6. The sound insulation is evaluated according to “EN ISO 717-1”.
Sound reduction index
The sound reduction index characterizes the airborne sound insulation of a component (incident sound power / sound power passing through). The sound insulation index R indicates the airborne sound insulation of a component without consideration of the construction-usual secondary paths.
The sound insulation index R’ denotes the airborne sound insulation of a component, taking into account the construction-typical secondary paths.
Weighted sound reducting index RW
The weighted sound reduction index Rw [dB] is used for the assessment of curtain wall facades. In thenth intervals, the sound reduction index for the individual frequencies of 50-5000 Hz is measured and recorded in a diagram. The resulting curve is aligned with a defined reference curve according to established rules. The value that the shifted reference curve has at 500 Hz defines the weighted sound reduction index RW. The calculated value RW,R is the value RW measured in the laboratory, which is referred to as the so-called “retention measure”. The provisional measure takes into account the ideal conditions in the laboratory compared to the installation situation on the construction site. For windows and facades: RW,R = RW – 2 dB. The resulting sound reduction index RW,res stands for the weighted sound reduction index of composite components. The value R’W describes the value measured in the installed state on the building, taking into account the side roads. The requisite sound insulation index erf. R’W specifies the requirement for the element that is functionally integrated in the building.
Spectrum adjustment values C and Ctr
The correction values are used to detect certain frequencies and are to be added to the RW value. Different noise sources are detected.
Adjustment value C (living area):
- Living activities (speeches, music, TV, …)
- children’s games
- Rail transport (medium and high speed)
- Car traffic >80 km/h
- Jet plane at a small distance
- Companies that emit mainly medium and high-frequency noise
Adjustment value Ctr (traffic noise):
- Urban traffic
- Rail traffic (low speed)
- propeller plane
- Jet plane at a great distance
- Disco music
- Companies that mainly emit low and medium frequency noise
Marking according to DIN ISO 717-1
RW(C;Ctr),complete statement of the sound insulation of a component
The area from C and C tr is between 0 and -10 dB.
RW(C;Ctr) = 43(-1;-4) dB
RW + C = 42 dB (Living area)
RW + Ctr = 39 dB (Road traffic)
RW,R + C = 40 dB (Living area)
RW,R + Ctr = 37 dB (Road traffic)
|Noise level range||Relevant external noise level||Room types|
|Bed rooms in hospitals and sanatoriums||Lounges in apartments; Overnight rooms in tourist accommodation; Classrooms and the like||Offices 1) and the like|
|dB(A)||erf. R’W,res of the external component in dB|
|II||56 bis 60||35||30||30|
|III||61 bis 65||40||35||30|
|IV||66 bis 70||45||40||35|
|V||71 bis 75||50||45||40|
|VI||76 bis 80||2)||50||45|
The outside noise level is set according to the norm depending on the noise source.
Furthermore, the standard describes correction coefficients for the required resulting sound insulation index erf. R’W,res in the ratio of the total area of the external component (SW+F) of a room to the base area SG of the room.
|(SW+F ) /SG||2,5||2,0||1,6||1,3||1,0||0,8||0,6||0,5||0,4|
Sound insulation classes according to VDI guideline 2719
The soundproofing measure describes the sound insulation of components.
|Sound insulation class||Required sound insulation index|
|measured on the construction facade||measured on the test stand facade||measured at the test stand glazing|
|R’W [dB]||RW [dB]||RW [dB]|
|1||25 – 29||≥ 27||≥ 27|
|2||30 – 34||≥ 32||≥ 32|
|3||35 – 39||≥ 37||≥ 37|
|4||40 – 44||≥ 42||≥ 45|
|5||45 – 49||≥ 47||1)|
|6||≥ 50||≥ 52||2)|
Filling the sound insulation of a curtain wall façade depends mainly on the used glazing. Soundproof glass and high-noise insulating panels protect the interior.
Measures to increase the sound insulation in the glazing:
- Increase of the glass mass
The heavier a disk is, the higher the sound insulation value is usually.
- Disc stiffness
The more elastic a disk is, the higher is the sound insulation value as a rule.
- Asymmetric disc structure
Insulating glass with asymmetrical design reduces the influence of the natural frequency.
Since coincidence breaks * are also at different frequencies, a significant improvement in sound insulation is achieved.
- Laminated safety glass panes with special PVB acoustic foils
The intermediate layers of PVB cause softer shells and thus less striking coincidence break-ins.
- Gas filling in the space between the panes
Depending on the specific structure, the use of noble gases improves the sound insulation.