Each layer of the iceberg contains a different kind of artifact. The depth sound measures how far your cell penetrates into each layer.
Paste a cell and click "Sound Depth" to measure.
In maritime terms, sounding is the act of measuring water depth. A ship "sounds" by lowering a lead weight on a line until it hits bottom, then reading the depth off the marked line. This tool applies the same metaphor to Quilt cells: we measure how deep a cell goes through the layers of the iceberg.
A cell's depth is the sum of how it touches each stratum. A cell that only appears in one repo is shallow. A cell that has a full substrate stack, uses multiple primitives, and hits impossibility bounds is abyssal.
The depth score is computed as: D = 0.1·tip + 0.15·surface + 0.25·middle + 0.3·deep + 0.2·abyss. See Paper 30: Sounding the Iceberg for the full methodology.