Evaluation of a physical method for estimating speech intelligibility in auditoria

The physical measure RASTI (Rapid Speech Transmission Index) has been developed for assessing speech intelligibility in auditoria. For evaluating this method, a set of fourteen auditorium conditions (plus two replicas) with various degrees of reverberation and/or interfering noise were subjected to: (1) RASTI measurements, (2) articulation tests performed by laboratories in eleven different countries. The various listening experiments show substantial differences in the ranking of the fourteen conditions. For instance, it appears that the absence of a carrier phrase in some of the articulation tests has great influence on the relative importance of reverberation as compared to noise interference. When considering only the tests using an appropriate carrier phrase (seven countries), it is found that the RASTI values are in good agreement with the mean results of these articulation tests.