SI-SDR (Scale-Invariant Signal-to-Distortion Ratio)

Scale-Invariant Signal-to-Distortion Ratio (SI-SDR) is a refinement of the SDR metric that removes the effect of overall volume (scale) differences, so a correctly separated stem isn't penalized or flattered simply for being louder or quieter than the reference. This makes it a more robust, widely adopted measure of source-separation quality in research. As with SDR, higher is better.