Development of binaural speech transmission index

Although the speech transmission index (STI) is a well-accepted and standardized method for objective prediction of speech intelligibility in a wide range of-environments and applications, it is essentially a monaural model. Advantages of binaural hearing to the intelligibility of speech are disregarded. In specific conditions mis leads to considerable mismatches between subjective intelligibility and the STI. A binaural version of the SIT was developed, based on interaural cross correlograms, which shows a considerably improved correspondence with subjective intelligibility in dichotic listening conditions. The new binaural STI is designed to be a relatively simple model which adds only few parameters to the original standardized STI, and changes none of the existing model parameters. For monaural conditions, the outcome is identical to the standardized STI. The new model was validated on set of 39 dichotic listening conditions, featuring anechoic, classroom, listening room, and cathedral environments. For these 39 conditions, subjective intelligibility (CVC-wordscore) was measured, as well as the binaural STI. The relation between binaural STI and CVC-wordscores in dichotic listening conditions closely matches the STI reference curve (standardized relation between STI and CVC-wordscore) for monaural listening. The monaural STI performs poorly in these cases