Airborne sound is the name given to the part of the sound emitted by the source that is propagated by the ambient air.
Wall construction and reduction of sound level
The aim of a sound protection construction is to remove as much vibrational energy as possible from the sound as it arrives. The walls of our booths are constructed to provide the optimum combination of a deformable outer shell and an absorbing layer so that as much of the airborne sound as possible is absorbed as the sound passes through the wall.
Depending on the particular purpose, you can choose between different levels of sound insulation provided by the construction of the walls.
Measuring the level of airborne sound
In order to obtain reproducible measurements that can be compared with other sound-absorbing techniques, a pre-defined signal is used for measuring airborne sound. This signal has a known strength and the tests measure how much it is reduced. All the measurements are conducted in accordance with the standards required by law and are determined by independent sworn experts.
The greater the value of the “rated noise level difference” Dn,w, the greater the reduction of the sound level.
The reduction of the sound level varies depending on the frequency range: the value given for the rated noise level difference takes into account the different physical absorbing behaviour at the different frequencies.
Measurements and graphs
The efficacy of an acoustic technique in relation to the airborne sound is usually given as the noise level difference, i.e. the difference between the levels in the source room and the receiving room. The important parameter is the rated noise level difference (Dn,w).
The measurements are shown in two-dimensional graphs with the noise level difference plotted on the vertical y axis, and the frequency on the x axis in intervals of thirds. A curve drawn through the points indicating the individual measurements shows the noise level difference changing with the frequency.
The pairs of numbers (co-ordinates) for the individual measurements are also given in a tables next to each diagrams.
The following measured values are available:
Noise level difference System ZS / ZSW
The following graph shows the standard noise level difference of a booth with the double-shelled, completely decoupled wall constructions System ZS and System ZSW (inner shell with angled walls for higher diffusion).