For the present study, the extension from the 0.3 - 3.4 kHz range towards higher audio frequencies was considered. The employed ABWE algorithm follows the source-filter model of speech production. Techniques for Artificial BandWidth Extension (ABWE) aim to extend the limited audio bandwidth of current narrowband telephone systems (0.3 - 3.4 kHz) towards the wideband frequency range (0.05 - 7 kHz). In several studies, a consistent quality advantage of the enhanced signals over narrowband speech is reported. In this contribution the authors evaluate an ABWE algorithm under realistic conditions and assess its impact on the speech intelligibility.