Predicting the spatial decay of speech intelligibility in open spaces is a subject that acousticians are far from having covered, even though it constitutes a key step in many architectural acoustics projects.

Enclosed spaces are often an object of study in terms of acoustics and have been in the past the aim of the development of the Module 9 of SILDIS® software (prediction of sound decay in enclosed spaces) which does not, however, allow the consideration of screens such as barrier walls, furniture storage in open areas (open spaces) where they are nevertheless often present.

Indeed, in such work areas, there is often held to prevent or correct the adverse effects of certain adjustments in terms of acoustic comfort e.g. spatial sound decay limited because of the short distances involved for sound propagation, poor discretion between workstations, preponderance of direct sound waves being not mitigated by absorbent surfaces being too far, resulting in increased noise levels of each speaker to be heard.

Obstacles must then oppose the propagation of noise from a workstation towards a neighboring workstation (in addition to furniture and storage units: separations, possibly of moderate height between workplaces belonging to the same subset, and with a higher height between workplaces areas sets) which, if they are absorbent, also contribute to limiting the amplification of sound levels in relation to the reverberation phenomena.

The acoustic performance of such obstacles to sound propagation must be taken into account for the design of premises for which the sound ambiance must be controlled.

ITS has integrated the prediction of the spatial decay of speech in open spaces to the simulation software SILDIS®.

Computation routines have been implemented for the simulation of the spatial decay rate of speech and of the A-weighted sound pressure level of speech at a distance of 4 m, which are usual indicators for the characterization of the sound quality of an open space.

Following the modification operations of the acoustics calculation software SILDIS®, the comparison of simulation results with bibliographic data (results of measurements, results of calculations by others ...) has shown a satisfactory agreement of output data of the Module 9 SILDIS® software thus created: for open spaces with various dimensions and properties of absorbent surfaces areas and when considering screens size appropriate to different concrete cases.

The expected result of improvements to the software SILDIS® (for predicting the spatial decay of speech intelligibility in open spaces) is an improvement of the accuracy of the assessment of the sound quality of open workspaces with screens in the context of protection of workers against noise in relation to the acoustic comfort in buildings.