Department of building structures, Czech Technical University, Ing. Jaroslav Hejl, Ing. Jiří Nováček, Ph.D. sound insulation of energy efficient wood ‑ based façade panels

Contents  sustainable sound insulation  Road traffic noise  Airborne sound insulation of building envelopes  Traditional heavyweight walls  Multilayered lightweight structures  Sound insulation of Envilop façade  Conclusions

Sustainable sound insulation  Sound reduction index is greatly influenced by their mass per unit area  Increasing sound insulation: - raising areal density - introducing elastic layers into the structure  Sustainability finds ballance between sound insulation and material consumption

Road traffic noise  67 million exposed to long- term average noise levels exceeding L den = 55 dB in the largest European cities in 2007  Regarding the sound pressure levels, two different sound spectra were standardized in ISO )Living noise 2)Urban traffic noise  This would be a very important when comparing heavyweight and lightweight façades.

Sound insulation of envelopes Current:  apparent weighted sound reduction index R´ w (single number) calculated from 100 Hz to Hz However  Human perception from 20 Hz  increasing number of sources emitting low frequency noise and a greater use of lightweight multi-layered structures.  The need of new rating -extend frequency band -add correction for low frequencies For example R´ w +C tr,

Traditional heavyweight walls Mass law: where  m´is the surface mass (kg.m -2 )  fis frequency (Hz) Sound reduction index of 250 mm thick hollow block wall with surface mass 316 kg.m -2 (dashed line represents the mass law equation (1))

Multilayer lightweight structures  Modern constructions where  m´ 1 is the surface mass of 1 st element (kg.m -2 )  m´ 2 is the surface mass of 2 nd element (kg.m -2 )  d is the depth of the cavity (m)  The use of several thin layers instead of one single layer with the same total thickness reduces the bending stiffness and increases the sound insulation  By introducing the air cavity into the structure, a significant additional sound attenuation can be achieved  Positive effect of separation of the two leaves can be found for frequencies higher than f r, where the structure is acoustically doubled (see Fig. 3). Therefore the resonant frequency should be as low as possible (at least less than 70 Hz) Sound reduction index of 230 mm thick double plasterboard wall with surface mass of face sheets 18 kg.m -2 (dashed line represents the mass law equation (1))

Envilop - description

Acoustic testing  4 non-transparent panels  Joints sealed with rubber gaskets  with and without independent wall lining consisting of: -air cavity between façade panels and independent wall 25 mm, -steel studs CW50 with mineral wool 50 mm, -single layer of plasterboards 12,5 mm with surface mass 9 kg.m -2.

Sound insulation of Envilop facade  Envilop façade – multilayered structure with resonant frequency fr  57 Hz  R w increased with independent lining from 40 dB to 57 dB  On low frequencies the sound reduction index is almost the same  Smaller difference in case of extended spectrum (from 50Hz) Sound reduction index of Envilop façade (dashed line represents the mass law equation)

Conclusions  Different behavior of heavyweight and multilayered structures  Careful design of multilayered structures with considering road traffic  Highly evaluated according the current methodic.  Proposed methodic -extend frequency band -add correction for low frequencies would have a decisive effect on design of lightweight multilayered structures.

Department of building structures, Czech Technical University, Measurements presented in this presentation were supported by project No. CZ.1.05/2.1.00/ – University Centre for Energy Efficient Buildings, project No. CZ.1.05/3.1.00/ – Intelligent Buildings and project No.SGS15/010/OHK1/1T/11 Study of sound transmission through building elements with respect to the evaluation of sound insulation in buildings. Thank you for your attention