SPEECH COMMUNICATION INDEX METER: FURTHER APPLICATIONS AND IMPROVEMENTS
BOLT BERANEK AND NEWMAN INC CAMBRIDGE MA
Pagination or Media Count:
To study the feasibility of using the Speech Communication Index Meter SCIM to evaluate time-varying communication systems, recordings were made of the transmission characteristics of a troposphere-scatter system. At many specific points in time in these recordings, Articulation Indexes were calculated and intelligibility scores were obtained from listeners with the aid of a special test procedure. For most points, the intelligibility score could be reasonably well predicted from the Articulation Index. This finding was interpreted as indicating that SCIM is potentially capable of evaluating time- varying systems. In a second study, SCIM was used to predict the intelligibility of peak-clipped speech. For a wide range of signal-to-noise ratios and clipping levels, the performance of SCIM was compared with intelligibility test results reported in the literature. After a minor modification, SCIM computed reliable SCIs which could be related to the published intelligibility data. This study demonstrated that SCIM could accurately evaluate communication systems employing peak clipping. SCIM was also modified to reduce the computation time, and to improve the synchronization between the signal generator and the analyzer. In addition, various other circuit changes were implemented to improve the performance of SCIM.
- Test Facilities, Equipment and Methods
- Voice Communications