Open-plan rooms are an example of room design where the reverberation time must be supplemented with descriptors that are adapted to the room’s geometrical shape and that can provide guidance for the acoustical design. A central question regarding open-plan rooms is how the acoustic planning will affect the propagation of the sound in the premises and, thus, the acoustic comfort.
The main acoustic source of disturbance in an open-plan area is usually speech. It is therefore important that people who need to communicate sit near each other while, at the same time, different work groups must be sufficiently separated acoustically not to disturb each other.
The acoustic planning of an open-plan area requires that a number of factors should be taken into consideration, such as
location of work stations
choice of absorbent ceiling
design of furnishings (furniture, screens, wall absorbers)
silent work areas
work methodology and technical aids
In order to achieve acceptable acoustic conditions in an open-plan area at all, a sound-absorbing ceiling is a necessity. The ceiling must have a high absorption factor and be installed at as low a level as possible to have the best possible acoustic effect. The figure illustrates the fundamental significance of an absorbent ceiling. It shows that the ceiling reduces the sound level and increases the rate at which the sound level decreases over distance. This also means that the distance required between work stations in order to achieve an acceptable level, i.e. a speech level that does not disturb or distract, will be shorter.
In addition to reducing the sound level and increasing the reduction in sound level that occurs over distance, an absorbent ceiling will improve the function of screens and other screening furnishings. The degree to which a ceiling improves the effect of screens can be classified in an AC value (Articulation Class).