RASTI for speech isolation evaluation

In open offices, there is a demand for speech isolation. As it becomes more important to avoid surveillance from outside conference rooms, a reliable method of evaluating the speech security becomes necessary. Research has shown that transmission loss or the articulation index method does not give enough information. This is because speech intelligibility, or rather the lack of speech intelligibility, depends on more than the signal‐to‐noise ratio. The RASTI method takes into account the effects of reflections, reverberation, and noise. By using the low end of the RASTI scale, the lack of speech intelligibility can be determined. This paper describes the measurement, using elevated signal levels, as well as measurement results.