Fraunhofer Institute for Building Physics IBP
Acoustic semi-anechoic chamber for measuring the sound propagation and directional characteristics of a sound source.
Sound propagation in a semi-anechoic chamber
Acoustics
Measurement of sound propagation in an anechoic chamber
An environment with room acoustics optimized to reduce reflection is used to simulate the acoustic conditions of a free field above a reflecting plane. Such a room is classified as a semi-anechoic chamber. This environment can be used to perform highly accurate measurements of the radiated sound power from sound sources, as well as their directional characteristics. An acoustic free field is distinguished by the fact that the sound pressure level decreases proportionally with increasing distance from the sound source. This condition is achieved by lining walls and ceilings with special sound-absorbing materials, such as flat absorbers (industry) or wedge absorbers, as in this room. The chamber is about 20 meters long, which allows measurements of sound propagation over obstacles to be performed. Typical tasks include the measurement of sound diffraction or sound shielding via barriers, such as noise barriers, as well as the scattering or absorption of sound by acoustically relevant surfaces.
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| Measurement | Sound propagation, sound shielding and attenuation |
| Measurement object | Scale models of constructions, buildings and landscapes, for example sound screens and noise barriers |
Technical data
| Free room size (inside liner) (L × W × H) | 19,43 m × 5,25 m × 6,17 m |
| Room volume | 629 m3 |
| Entrance door (H × W) | 1,90 m × 2,37 m |
Special features
| Connection to a reverberation room | Measurement of sound insulation and sound absorption of elements between reverberation and anechoic room |
| Size of the connecting door (measuring surface) | 3,80 m × 2,35 m |
More information
- Scale model measurements (on a scale 1: 40), including rooms
- Determination of sound propagation in scale model landscapes and urban scenarios, for example emission and shielding of buildings, sound screens and noise barriers
- The ventilation unit and air conditioning system make it possible to simulate wind and temperature profiles via air vents in the corners of the chamber.
- Vibrational isolation by using “Omega Clamps” to suppress influence due to structure-borne sound
- Lower cut-off frequency 125 Hz (according to standard)