Behavioral entrainment is an important, naturallyoccurring dynamic phenomenon in human interactions. In this paper, we carry out two quantitative analyses of the vocal entrainment phenomenon in the context of studying conflictual marital interactions. We investigate the role of vocal entrainment in reflecting different dimensions of couple-specific behaviors, such as withdrawal, that are commonly-used in assessing the effectiveness on the outcome of couple therapy. The results indicate a statistically-significant relation between these behaviors and vocal entrainment, as quantified using our proposed unsupervised signal-derived computational framework. We further demonstrate the potential of the signal-based vocal entrainment framework in characterizing influential factors in distressed couples relationship satisfaction outcomes.