The name for the class of auditory digital resources given in [3.2.2 of the model](https://www.w3.org/TR/annotation-model/#classes) is "Sound". The mapping provided in the context document is ["Audio"](https://github.com/w3c/web-annotation/blob/gh-pages/jsonld/anno.jsonld#L24) Given that the documentation is normative, the "Sound" mapping should be added to the context document. Initially raised within [IIIF](https://github.com/IIIF/api/issues/2330)