• Acoustics

Acoustic calculation with FEM: Noise reduction on façades

Noise reduction on high rise buildings located in areas prone to noise nuisance is a challenge in urban locations. Regulations have tightened and local authorities impose stricter noise control regulation on newly developed buildings. The cost incurred with such noise reduction measures has also become a commercially important factor. Acoustic calculations with FEM (Finite Element Method) on building façades and related structures can help optimize the cost incurred for such measures and present an acceptable approach to the authorities. An example case is presented below.

The objective of this study was to simulate acoustics over a newly developed residential complex in Amsterdam. Due to the closeness to rail tracks the noise levels at the façade and balconies/loggia are relatively high. Therefore, the balconies and loggias must be fitted with sufficient glass and noise absorption material to reduce noise levels.

Standard techniques to reduce noise levels are the usage of glass panels to cover openings and rockwool to absorb noise inside the balcony/loggias. Conventional ways to calculate noise propagation make use of ray-tracing methods. The ray-tracing method is not accurate enough to calculate sound propagation and absorption through various materials in detail. This is possible with FEM and therefore this method is used to optimize the design of the sound reducing measures. Moreover, authorities have begun to demand FEM calculation for cases where noise levels are higher and more accurate calculations are needed to ensure the required reduction in noise is achieved.

The amount of glass panels and rockwool used was optimized while adhering to the noise level reduction of 12 dB required by the authorities. In order to achieve this full height glass panels were applied at each level. However, with FEM calculations we found that a 12db reduction could still be achieved with lower height panels at higher floor levels. As such the glass panel height at each floor is optimized, reducing costs while keeping the noise levels within limits. Eventually an average reduction of 1.6 m2 of glass panel per balcony was achieved, saving about 160 m2 of glass panels in total.

L-shape damper

Plan view showing a sound damper composed of glass panels and rockwool attached to the façade (top). Contours of acoustic pressure at 500 Hz calculated with FEM (bottom).

Noise reduction façade

Decibel reduction on the façade at various sound source angles and various frequencies for the L-shape noise reducer.

Calculation of sound levels at the balcony

3D drawing for balcony attached to the façade (top), FEM model (bottom left) and decibel reduction table (bottom right).

Optimizing glass on balcony

Glass height optimized per floor to achieve ~12 dB reduction at each level. Ana average of 1.6 m2 glass panel per balcony was saved.