Overlap Ratio

Overlap ratio describes how much of a recording contains simultaneous speech. At a 20% overlap ratio, a fifth of the speech in the recording has at least two people talking at the same time. It is a property of the recording as a whole rather than of any single interruption.

It is one of the strongest predictors of how hard a conversation will be to diarize or separate, since accuracy for most systems degrades as the ratio rises. Benchmarks such as LibriCSS provide sessions at controlled overlap ratios so that systems can be compared at each level rather than on an average that hides where they break down.