Monaural and binaural benefit from early reflections for speech intelligibility

The auditory system takes advantage of early reflections (ER’s) in a room by integrating them with the direct sound (DS) and thereby increasing the effective speech level. The energy, spectral content and direction of the ER’s are dependent on wall absorptions and room geometries and therefore different from the DS.

By using an ER pattern from a real room and reproducing it in a loudspeaker-based virtual auditory environment, the important characteristics of the ER’s can be preserved and the benefit from ER’s for speech intelligibility (SI) can be quantified. In the present study SI was measured in such a realistic sound field by varying the level of the ER’s and the DS of the speech signal independently.

The efficiency of the ER’s was then defined as the ratio of the useful ER energy and the total ER energy at the speech reception threshold (SRT). Furthermore monaural SI measures were performed to investigate if ER processing is a monaural or binaural effect.