  We investigate a speech enhancement method based on the binaural
coherence-to-diffuse power ratio (CDR), which preserves auditory spatial cues
for maskers and a broadside target. Conventional CDR estimators typically rely
on a mathematical coherence model of the desired signal and/or diffuse noise
field in their formulation, which may influence their accuracy in natural
environments. This work proposes a new robust and parameterized directional
binaural CDR estimator. The estimator is calculated in the time-frequency
domain and is based on a geometrical interpretation of the spatial coherence
function between the binaural microphone signals. The binaural performance of
the new CDR estimator is compared with three state-of-the-art CDR estimators in
cocktail-party-like environments and has shown improvements in terms of several
objective speech quality metrics such as PESQ and SRMR. We also discuss the
benefits of the parameterizable CDR estimator for varying sound environments
and briefly reflect on several informal subjective evaluations using a
low-latency real-time framework.
